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Jl Scries 0f Six l^ccturcs 







Printed by Edward Stanford, 55 Charing Cross, London, S.iy. 


The Science of Meteorology, as it is studied at 
the present day, may well receive the designation 
of " modern." Its renovation dates from the pro- 
posal to employ telegraphy in the transmission of 
meteorological observations, which proposal was 
realised hardly more than a quarter of a century 

As soon as observations collected by telegraphy 
were laid down on charts, an entirely new light 
was thrown upon the complex phenomena included 
under the simple term " weather " ; and by the 
publication of the charts so prepared, the public 
were admitted to the study of the processes of 
weather production by the mutual action of cyclones 
and anticyclones. The diffusion of this knowledge, 
however, is slow ; and it appeared to the Council 
of the Meteorological Society that a set of Lectures 

vi Preface. 

explanatory of modern views, and showing how 
the stock of knowledge of an older date may be 
thereby illustrated, would, in the present condition 
of the science, be well timed. 

Arrangements were made by the Council of 
the ]Meteorological Society to deliver in the autumn 
of 1878 the course of Lectures which are repro- 
duced in the following pages. 

The Council of the Institution of Civil Engin- 
eers most graciously lent the use of their theatre 
for the six evenings, and to that body the thanks 
of the r^Ieteorological Society are most gratefully 




By Robert James Maxn, M.D., F.R.C.S., F.R.A.S., F.R.G.S., 

Definition and object of meteorological science — Purpose 
and plan of this course of lectures — Meteorology based on the 
physical properties of the atmosphere — Invisibility of air — Its 
weight— Minuteness of particles — The gaseous state — Kinetic 
theory — Inherent movements of atoms — Compressibility of 
air — Expansion by heat — Contraction by cold — Influence of 
gravity upon its condition — The law of Boyle and Mariotte — 
Pressure increases in same ratio as volume — Regnault's law — 
The limits of the atmosphere — Highest ascents of balloon — 
M. Liais' views — Specific gravity of air — Specific gravities of 
mercury, water, and glycerine — Torricelli's invention of mer- 
curial barometer — Pascal's proof of Torricelli's views — Gly- 
cerine barometer of Mr. Jordan — Pressure of air in all directions 
— The same on all areas of equal size — Relation of area of 
cistern to area of column of barometer — Pressure in all 
directions the cause of wind-movement — Atmospheric pressure 
at sea-level — Diminution in higher regions of the air — Theo- 

viii Syllabus. 

retical depth of a homogeneous atmosphere — Pressure on a 
square foot and square mile — Weight of the entire atmosphere 
— Constituent elements of air — Oxygen and nitrogen — Law of 
gaseous diffusion — Vaporisation of water — Relations of aqueous 
vapour and atmosphere — Saturation varies with temperature 
— Capacity of air for aqueous vapour doubled with each 
increase of 27° of temperature — Elastic force of atmospheric 
vapour — Determining cause of clouds and rain — Influence of 
aqueous vapour of the air on the barometer — Influence of 
evaporation on temperature — Evaporation causes cold — Con- 
densation sets free heat — Warmth promoted by rain — Cause 
of low temperature of high regions of the air — Limiting tem- 
peratures of atmosphere — Diathermancy of dry air — Aqueous 
vapour acts as a heat screen — Scorching sunshine of mountain 
tops — Softened character of tropical heat — Atmospheric car- 
bonic acid and ammonia — Fixity of constitution of atmosphere 
— Ozone, a modified condition of oxygen — Transparency of air 
— Importance of diathermancy and transparency to terrestrial 
life — The blue sky dependent on atmosphere — Cause of sun- 
set colours. 



By John Knox Laughton, M.A., F.R.A.S., F.R.G.S., F.M.S., 
Mathematical Instnictor and Lecturer in Meteorology at the Roya) 
Naval College, Greemvich. 

Importance of climatic knowledge — Air temperature a ver)' 
important component of climate — Temperature of space — 
Earth temperatures — Sun the sovu-ce of all heat as affecting 

Syllabus. ix 

climate — Isotherms do not agree with parallels of latitude — 
Marked instances of this — Isothermal maps — Causes of the 
disagreement : soil, aspect, shelter, ocean currents ; with 
geographical examples — Heat carrying power of air, as com- 
pared with heat of water — The Sahara submerged — Hot winds : 
the Swiss Fohn ; Arctic observations ; The Prairies of North 
America — Cold winds and cold spells, as in Texas, Minnesota, 
Paraguay, the Valley of the Amazon — Our English " Black- 
thorn winter " — Effects of moisture or dryness on radiation — 
Equable and excessive climates — Range of temperature by day 
and night, summer and winter — Mean alone gives little idea of 
climate : the range and the extremes have a most important 
influence on animal and vegetable life : Grapes in northern Asia ; 
Corn in the Hebrides ; Tropical Ferns in Tierra del Fuego ; 
Vineyards of the Gironde — Sensations are ver}' incorrect 
indication of temperature : Arctic experiences ; heat at Hong 
Kong — For scientific comparison, exact measurement necessary. 
Thermometers — Methods of observing — Sun and shade — 
Difficulties to be contended with — Different screens — Thcrmo- 
vietre frondc — Thermographs — Maximum and minimum — 
Methods of obtaining means. 



By Richard Strachan, F.M.S. 

Historical notice of the invention and perfecting of the 
barometer — Meteorology mainly concerned with standard 
barometers — Fortin's standard for stations — Kew-pattern 
marine barometer a standard for use at sea — Gay Lussac's 

X Syl/abas. 

s)'phon a standard for travellers — Relative merits of these as 
regards accuracy and permanence of errors — The Kew-pattern 
Barograph — What the barometer has told us — Popular use of, 
as a weather glass — The aneroid a substitute for the barometer 
— Use of, in measuring heights and contouring. 

Distribution of atmospheric pressure in storms — Average 
distribution of pressure over the globe — Diurnal range of pres- 
sure — Atmospheric pressure correlated to temperature, wind, 
and weather — Science here evident, though the key to pre- 
diction may be wanting. 



By the Rev. \Y. Clement Ley, M.A., F.M.S. 

Causes of the small amount of progress hitherto made in 
this branch of Meteorology' — No very satisfactory classiiication 
of cloud varieties at present exists : the old nomenclature in- 
complete ; but it would be as yet premature to remodel it 
— Cloud types related to the electrical conditions on the one 
hand, and on the other to the types of wind and pressure dis- 
tribution — Probable outlines of a future science of Cloud Laws 
— Scientific explanations of the best-known prognostics derived 
from the sliapfs, colours, etc., of the clouds — Value of the 
knowledge obtained from the movements of the clouds — Rela- 
tion of indications derived from the clouds and from Weather 
Charts — Value of the less-known weather signs dependent on 
this relation — Special instances of the application of this study 
in the actual conditions of particular days — Method and limits 
of this kind of weather-forecasting. 

Syllabus. xi 


By George James Symoxs, F.R.S., Hon. Sec. M.S. 

Rain : What it is — Where it comes from — Why it falls — 
How it is measured — Different patterns of rain gauges — Best 
size, shape, pattern, and material for rain gauges — Mechanical 
gauges — Storm gauges — Necessity for inspecting rain gauge 
stations — Collection of rainfall statistics — Applications of rain- 
fall data to practical life — Drainage — Flood warning — Water- 
works — Salmon catching — Sugar making — Effect of altitude 
on rainfall — Details of mean fall in British Isles and at some 
Foreign Stations — Seasonable distribution — Daily fall — Storm 
rains — Secular variation. 

Snow : What it is — How it is measured — Its beautiful 
crystallisation, and how to observe it. 

Hail : What it is — Some of its forms — Noise before it falls 
— -Rarity at night. 

Atmospheric Electricity — Thunder-storms — Lightning 


the nature, methods, and general objects of 

By Robert H. Scott, M.A., F.R.S., F.G.S., For. Sec. M.S., 
Secretary to the Meteorological Council. 

Meteorology the Science of the Atmosphere, and therefore 
under great disadvantages as compared with Astronomy — 

xii SyllabiLs. 

Stations must be multiplied to eliminate effect of local con- 
ditions — Observations must be continued for a long time to 
confer any value on results derived from them — Meteorology 
demands the knowledge of many other sciences, especially 
Chemistry and Physics — Determination of the amount of 
moisture deposited from the atmosphere, and available on the 
earth for mechanical work, an immediate point of contact 
between Meteorology and practical Engineering, etc. 

Determination of the Temperature, Pressure, and motion of 
the Air, as well as of the changes in its constitution produced 
by the variations in the amount and condition of the Aqueous 
Vapour — Difficulties from the impossibility of extending the 
sphere of observations to an appreciable extent above the 
surface of the earth. 

Objects of Meteorology almost countless — Air and its con- 
dition — Its influence on health, the growth of crops — Value 
of attaining the slightest approach to a knowledge of what the 
weather will be for even a week in advance not only to the in- 
dividual, but to the country and to the world at large — Clima- 
tology as affecting the choice of colonies, and what products 
to expect from them — Sanitary Meteorology shows under what 
conditions life can best be prolonged and health maintained. 



1. Definition and Objects of Meteorological Science. 

Whatever may be thought of the proceedings of 
meteorologists, there can be no rational question as to 
the loftiness of their aim. This is indeed expressed in 
the name of their science. The word Meteorology is 
derived from the old Greek term " fierecopo';," which 
signified elevated or soaring. The name has not 
been adopted, as it has sometimes been erroneously 
conceived, because meteorologists at one time busied 
themselves with observing the " falling stars " or 
" meteors." The word, as a matter of fact, was used 
in very much the same sense as that in which it is 
now applied, by Aristotle, 300 years before Christ. 
In a treatise which he composed under the title 
" MerecopoXoytKa," he dealt with all which was at that 
time known concerning water, air, and earthquakes. 
At the present time the object of Meteorology is 
properly the scientific study of atmospheric phenomena, 
and the investigation of weather and climate. The 

2 Meteorological Lectures. 

base of the science is, therefore, an exact and adequate 
acquaintance with the physical properties of the atmos- 
phere ; and these, in consequence, have been taken as 
the appropriate subject for the Introductory Lecture 
of a course, in which it is the primary aim to furnish 
a popular explanation of the great leading features of 
meteorological phenomena. In dealing with this intro- 
ductory phase there is, however, one difficulty which 
stands in the lecturer's way. He is placed from the 
first, as it were, upon the horns of a dilemma, because 
there is danger on the one hand that he may assume 
too much knowledge on the part of a mixed audience, 
and so soar beyond the easy apprehension of one 
portion of his hearers ; or, on the other hand, that he 
may render himself tedious to another portion by 
dwelling too much upon elementary conditions and 
facts. The best method to adopt in such circumstances 
is probably to have due regard to both sides of the 
dilemma, and to endeavour to steer a midway course. 
That, at any rate, is the solution of the difficulty which 
the lecturer intends to attempt upon this occasion. 

2. The Invisibility and Substantiality of Air. 

The air is invisible to the eye in its purest state, 
on account of its great transparency. It is, neverthe- 
less, a really substantial body in itself This is suffi- 
ciently proved by the mechanical impulse which it is 
able to communicate when in motion. It drives round 
the spirally-adjusted sails of the windmill ; it forces 
along over the water heavily-laden ships ; it strikes 

The Physical Properties of the Atmosphere. 3 

against the sensitive cheek of any person standing in 
its way with a blow which can be felt. But the fact 
is more scientifically demonstrated by showing that 
air has weight. If 6 cubic feet of air be condensed 
or compressed into an iron bottle, and the bottle be 
closed with a screw cap, and placed in one pan of a 
pair of scales, it may be so balanced there as to give 
the weight of the iron bottle, of the air which that 
originally contained, and of the additional 6 cubic 
feet of air w^hich has been compressed in. If, in 
such a position of affairs, the neck of the bottle is un- 
screwed, the 6 cubic feet of compressed air rush out 
in a stream, and the scale pan rises as the air 
escapes. The counterpoise which will then have to 
be added to the scale to restore the balance is 
obviously the measure of the weight of 6 cubic feet 
of air. Or yet, again, a glass globe holding 4 quarts, 
or 100 cubic inches, may be first weighed when full 
of air, and then again when the air has been pumped 
out. The difference of weight in such case will be 
as manifestly the weight of 100 cubic inches of air. 
100 cubic inches of air, when the barometer stands at 
29-92 inches, and when the temperature is 32° Fahren- 
heit, weigh 32*58684 grains. A cubic foot weighs 
573*5 3 grains. Thirteen cubic feet, or a quadrangular 
block measuring 24 inches in two directions and 39 
inches in the third, weighs exactly i lb. A room 10 
feet square contains yj lbs. of air. Westminster Hall 
holds 75 tons. Air is about 760 times lighter, bulk 
for bulk, than water. 

Meteorolos'ical Lectures, 

3. Its Gaseous State. 

The smallest particles, or ultimate atoms, of air are 
so minute that no single one of them can be seen when 
in isolation from its companions. Each is smaller than 
the minutest speck of substance which is visible to the 
human eye when aided by powerful microscopes. By 
the help of microscopes solid particles can be seen which 
are only the 8o,oooth part of an inch across. It is 
certain that the ultimate atoms of air are very much 
smaller than that. No one can yet say how much 
smaller ; but Sir William Thomson, who has made 
some very subtle investigations in regard to the mole- 
cular condition of matter, believes that the atoms of air, 
and of all gases, are so small that not less than 
500,000,000 of them could be ranged in a line within 
the extent of an inch. The atoms of the air, neverthe- 
less, are suspended many times their own diameters 
asunder. They do not touch each other, but float 
freely apart, repelling each other very energetically 
when the attempt is made to drive them mechanic- 
ally into close quarters. Sir William Thomson has 
expressed his opinion that there are some circumstances 
connected with his investigations which seem to indicate 
that as many as 100,000,000,000,000,000,000,000 
atoms are contained in a single cubic inch of any gas. 
Such figures far transcend the powers of most minds to 
deal adequately with them. But they help, at any 
rate, to impress upon the attention the fact that the 
atoms of the air are of an exceeding minuteness. 

The Physical Properties of the Atmosphere. 5 

4. Compressibility of Air. 

It is one consequence of the atoms of air being 
thus freely suspended apart from each other, that they 
can be driven, to some extent, into closer neighbour- 
hood by the application of mechanical force. This 
leads to what is termed the compression of air — the 
mechanical squeezing of it up into smaller volume. 
Air which is contained in a syringe without outlet can 
be squeezed in, in this way, by pressing down the 
piston upon it, either by the hand, or by loading 
it with a weight. If double the force is applied 
in this way to air in a closed syringe, its volume 
is diminished one half. This is one characteristic 
which distinguishes a gas from a liquid. Gas is 
very largely compressible, and liquid very slightly so. 
The pressure which would make any given volume of 
gas contract its bulk one half, would cause a similar 
volume of water to diminish only by the xoim'ooo^'^ 
part, or about the 5 oW^^ °^ ^^^ bulk. The contraction 
of air under pressure is, however, subject to the influ- 
ence of a fixed law, which has been investigated by 
various able experimenters. It was examined towards 
the end of the seventeenth century by a Burgundian 
priest, named Edme Mariotte, who dwelt at Dijon, and 
died there in 1684 ; and also by the English philosopher, 
Robert Boyle, who was one of the members of the 
First Council of the Royal Society, This law has 
consequently come to be spoken of indifferently as 
Mariotte s and Boyle s law. It applies equally to all 

6 Meteorological Lectures. 

kinds of gases, as well as to the atmosphere. In its 
simplest form of expression, it merely affirms that the 
volume of a gas is invariably diminished to one half 
by doubling the pressure to which it is exposed. It 
will be observed that it is a consequence of this law, 
that air constantly resists more vigorously as it is 
driven into smaller and smaller bulk, very much as a 
strong spring would do upon being more and more 
bent. A pressure of 30 lbs. upon the square inch 
would reduce lOO cubic inches of air into 50 cubic 
inches. But 60 lbs. would then only reduce the 50 
cubic inches into 25. 

Whenever the force which has produced condensa- 
tion in a gas is removed, the gas immediately recovers 
its original volume, in consequence of the several atoms 
energetically repelling each other when they are driven 
into preternaturally close quarters. This property of a 
gas to recover its original volume when mechanical 
pressure is removed, is, in familiar language, termed its 

It is an important consequence of the compressibility 
of a gas, that in any given bulk the lower part is 
compressed, or squeezed in, by the weight of the atoms 
which rest above. Thus, in a room full of air the 
lower layers have their atoms squeezed more closely 
together by the weight of the layers which rest above. 

5. Expansion by Heat. 

But the compression of air by the application of 
mechanical force is in some measure interfered with by 

The Physical Pi^operties of the Atmosphe7^e. 7 

the influence of heat. Increase of temperature expands 
all gases. This is well instanced in the very common 
experiment of causing a bladder only partially dis- 
tended with air to become tense and full by placing 
it in front of a fire. Here, again, the effect pro- 
duced by the addition of heat is capable of being 
expressed by a fixed formula, which is termed a law, 
and which has been investigated by various skilful 
experimenters. It was independently examined by the 
English philosopher Dalton and the French philosopher 
Guy Lussac, in the years 1801 and 1802 ; and in a 
memoir upon the subject, which Guy Lussac printed in 
1802, he stated that he had reason to believe the 
same investigation was entered upon fifteen years 
before by Mons. Charles, who was Professor of Physics 
in the Conservatoire des Arts et Metiers, and who is 
famous as having first employed pure hydrogen gas for 
the inflation of balloons. On account of this statement 
of Guy Lussac's it has become common, in recent times, 
to speak of this law of the expansion of gas as the law 
of Mons. Charles.^ It is also alluded to sometimes as 
Regnault's law, because the French philosopher of that 
name subsequently improved upon Guy Lussac's ex- 
periments, and made the numerical statement of results 
more exact. 

Guy Lussac's statement of this law was to the 
effect that air, and other gaseous substances, increase 
their volume by the 4^9th part of their bulk for each 

1 See The N'ew Chemistry, by Josiah P. Cooke, page 48 ; and The 
Theory of Heat, by Clerk Maxwell, page 29. 

8 Meteorological Lcchircs. 

degree of Fahrenheit which is added to their tempera- 
ture. Regnault's correction of this gave the quantity 
of ^rnr-^^^"^ P^^'^ °^ '^^ ^^^^ ^°^ ^■3ic\x degree, and this is 
now universally accepted as the more correct estimate 
by scientific men. When air is heated from the tem- 
perature of ice to that of boiling water, lOO cubic 
inches become 1366-5 cubic inches. 

The kinetic, or kinematic,^ theory of the gaseous 
state describes the atoms of gases as being in a condi- 
tion of incessant movement, and when contained in a 
closed vessel as clashing to and fro in all directions 
and so coming into frequent collision among them- 
selves, and continually striking against the sides of the 
vessel. The pressure produced upon the containing 
vessel by the so-called elasticity of the gas is attri- 
buted to these movements, and it is believed that the 
increased elasticity resulting from augmented heat is 
due simply to the fact that the atomic commotion is 
quickened and rendered more energetic by any rise of 
temperature. It has been calculated that atoms of 
hydrogen gas, under a barometric pressure of 30 
inches, and at a freezing temperature, perform their 
kinematic dance, in this way, with a velocity of not less 
than 6097 feet per second. 

6. Rarefaction of the Atmosphere in High Regions. 

In consequence of the expansion which results in 
air from diminished pressure, the atmosphere gets more 
rare in its higher regions in proportion as it is there 

1 From KtV7;/;ta = motion. 

TJic Physical Properties of the Atmosphere. 9 

less influenced by the air-weight above. At an eleva- 
tion of 3 miles, which is a trifle more than the 
summit of Mont Blanc, one-half the superincumbent 
weight has been left below, and any given bulk of air 
accordingly expands to double the volume which it 
had at the sea-level. At 6 miles of elevation the 
volume is again doubled. At 60 miles the air is 
probably as rare as the best vacuum that can be pro- 
duced by the air-pump. It is quite impossible, how- 
ever, for any direct observation to be made at such 
elevation, because no man can continue to breathe and 
live in air so rare. Mr. Glaisher once ascended in a 
balloon to 37,000 feet, or nearly 7 miles, but he 
was rendered insensible at a height of 29,000 feet ; 
and he and his companion, Mr. Coxwell, owed their 
lives to the fortunate circumstance of the escape-valve 
of the balloon having been opened before actual insen- 
sibility came on. All animal life would certainly be 
destroyed at a height of 8 miles. 

The question as to where the outward limit of the 
atmosphere exists, is therefore one that has to be 
entirely dealt with by reasoning upon theory. Some 
authorities conceive that there can be no air beyond 
eighty miles above the sea-level. In consequence of 
some observations recently made upon the influence of 
the rarer regions of the air upon twilight at Rio 
Janeiro, a competent investigator, M. Liais, infers that 
the air extends for 190, and possibly for 212, miles 
from the sea-level. 

lO Meteorological Lectures. 

7. The Weight of the Atmosphere. 

The weight of the air, which has been already 
spoken of, is a very different thing from the weight 
of the atmosphere. This means, not the number of 
grains which any given volume of air, such as that 
which can be contained in a pint bottle or in a large 
room, weighs, but the weight with which a column of 
air of some definite diameter, and extending quite to 
the highest limit of the atmosphere, presses down upon 
the earth's surface. The weight of the atmosphere, in 
this sense, was first ascertained by the Italian philoso- 
pher Torricelli, a pupil of Galileo, about the year 1643. 
He took a glass tube which was open at one end and 
closed at the other, and which was several inches long, 
and turning it mouth upwards he filled it with the liquid 
metal quicksilver, or mercury. Then placing his finger 
firmly over the open end of the tube, he turned the 
upper end down, plunged it into a cistern or vessel 
filled with mercury, and then carefully removed his 
finger, so that the mercury in the tube and that in 
the cistern came into continuous contact. When the 
inverted tube was held perpendicularly upwards after 
this operation, he found that the mercury in the tube 
sank down until its upper end was just 30 inches 
above the surface of the mercury in the cistern, and 
then stood there, leaving an empty space at the top of 
the tube. He explained this curious result by the 
conception that the 30 inches of mercury within the 
tube was kept up in a balanced state by the weight 

The Physical Propej'iies of the A tmosphere. 1 1 

of the column of air which pressed upon the surface of 
mercury in the open cistern ; and his explanation proved 
to be correct, for when Pascal, another experimenter, 
caused the apparatus to be carried to the summit of the 
Puy de Dome, a mountain in France some 3500 feet 
high, it was found that the column of mercury was there 
only sustained 27, instead of 30, inches, because at the 
summit of this mountain a tenth part of the entire 
weight of the column of air had been left beneath. 

This experiment of Torricelli's was, in reality, the 
invention of the barometer, the noble instrument which 
is now of such vast service to meteorologists.^ 

When this experiment is performed with a tube 
which has a transverse area amounting to exactly i 
square inch, every 2 inches of the column of mercury 
in the tube weigh i lb. The 30 inches of the column, 
therefore, weigh i 5 lbs. It hence appears that a column 
of air of i square inch sectional area, carried up to the 
very highest limit of the atmosphere, has exactly the 
same weight as a column of mercury 30 inches high, or 

1 The actual experiment which was performed in the first instance 
by Torricelli, and which led to the invention of the barometer, was of a 
somewhat more complicated character. A glass tube 6 feet long was 
filled with mercuiy, and then inserted so as to place its mouth beneath the 
upper surface of a reservoir of the same liquid metal, with water cohering 
it to some distance above. Upon uncovering the mouth of the tube, 
which had been stopped by the end of the finger during the immersion, the 
column of mercury in its interior fell until about 30 inches above the 
mercurial surface in the reservoir ; and when the tube was so raised that 
its mouth was above the mercury in the reservoir, the liquid metal at once 
ran down out of the tube, and the water, which still covered the mouth of 
the tube, then rushed up into the vacuous space until it filled the 6-feet- 
long tube to the top. 

1 2 Meteorological Lectures. 

in other words, that it also weighs i 5 lbs. If the air- 
column were homogeneous all the way, instead of 
expanding and getting rarer with height, as it does in 
consequence of being a gaseous substance, it would 
counterpoise the 30 inches of mercury at a height of 
26,214 ^6Gt, or nearly 5 miles. Air is nearly 11,000 
times lighter than the same bulk of mercury. It really 
takes something beyond 80 miles of air to make the 
counterpoise, because the air is not homogeneous, but 
stretches itself out rarer and thinner as it gets higher 
and higher. 

The open cistern of mercury in Torricelli's experi- 
ment was considerably larger than the closed tube 
holding the column of mercury ; and yet the large 
air-column, many inches across, which pressed down 
upon the upper surface of the cistern, was effectually 
counterbalanced by the narrow mercurial column in 
the tube. The reason for this result is, that only so 
much of the air as represents a column of the same 
diameter as the mercury in the tube, is sustained by 
that column of mercury. All the rest of the air-column 
is supported upon the rigid bottom of the cistern. It 
is one of the fixed conditions of fluid pressure that this 
should be the case. The size of the column of mercury 
determines for itself bow much of the air-column shall 
be practically brought into active antagonism, or 
counterpoise, with it. 

The pressure of the atmosphere amounts to a very 
considerable force when large spaces have to be taken 
into account. The pressure, which is only 1 5 lbs. 

The Physical Propei'ties of the Atmosphere. 13 

upon a square inch, is 2 160 lbs., or nearly i ton, 
upon a square foot, and 263,000,000 tons upon a 
square mile. The great pressure caused by the air is 
familiarly shown by its bursting a bladder tied tightly 
over the mouth of a thick glass cylinder, when all the 
counterbalancing air is pumped away from beneath. 
1 5 lbs. upon the square inch is technically spoken 
of as one atiiiospJiere of pressure, because that is the 
force with which the atmosphere presses upon each 
square inch of the earth's surface. 

The atmosphere, taken as a whole, weighs about 
the 1200000 ^^ P^"^^ °^ ^^^ entire terrestrial sphere. 

The atmosphere, however, does not always press 
down upon the earth with the same force. There is a 
less weight of air over a given place sometimes than 
at others. When, for instance, the air gets greatly 
heated by the sunshine over some one spot of the 
earth's surface, it expands under the influence of the 
heat, and becomes lighter. The difference in the 
weight of the atmosphere from this cause amounts 
often to more than \ lb. upon the square inch. Such 
difference is at once indicated by the rise or fall of the 
column of the barometer, which stands sometimes 
more than an inch higher than it does at others. 
When the atmosphere becomes more dense and heavy, 
the mercurial column of the barometer rises in the 
glass tube, and when the atmosphere becomes rarer the 
column of the barometer falls. It is this rise and fall 
of the column of this instrument from hour to hour, 
and from day to day, which is termed the oscillation 
of the barometer. 

14 Mcteoi'ological Lectures. 

But over and above this, the atmosphere does not 
press with equal force upon different parts of the earth 
at any fixed instant of time. The barometer shows 
that the air pressure may be great at one place at the 
same time that it is very much less at some other place 
only a few miles away. There are areas of high 
pressure and low pressure distributed side by side over 
the earth. 

The meteorological use of the barometer is princi- 
pally confined to the measuring of these differences of 
atmospheric pressure, either simultaneously, as they 
obtain on different parts of the earth, or in succession, 
as they follow each other at one spot. In both 
instances the differences indicate conditions of the 
atmosphere, and alterations in those conditions, which 
are intimately connected with vicissitudes of weather. 
The barometer is employed in meteorological investiga- 
tions, not to measure the weight of the atmosphere, 
but to ascertain the changes which occur in that weight 
from time to time, and the difference of that weight at 
different places. Wind, rain, cloud, sunny warmth, and 
wintry cold are all circumstances which are ruled by 
the var}-ing atmospheric states indicated by 
oscillations of the barometer. 

8. The Glycerine Barometer. 

Glycerine, or indeed any other liquid, might be 
used in a closed tube as a counterpoise to the column 
of the atmosphere, instead of mercury. But the column 

TJie Physical Propei'tics of the Atmosphere. 1 5 

in the tube would need, in the case of such a liquid as 
glycerine, to be 28 feet high instead of 30 inches. 
Few liquids are fit for the formation of barometers, 
because vapour rises from them into what should be 
the empty space at the top of the tube, and so embar- 
rasses the action of the instrument. Glycerine is one of 
the best liquids of light weight which can be employed 
for the construction of a barometer, because it has a 
vapour of low tension, which does not readily rise like 
the vapour of water. It does not boil until it is raised 
to a temperature of 290° Fahrenheit. A very ingenious 
glycerine barometer was actually constructed by Mr. Jor- 
dan for the recent Loan Exhibition of Scientific Instru- 
ments at South Kensington. It was fixed in one of the 
staircases, and the main tube was an ordinary metal gas 
tube, ~^ths of an inch in diameter, joined at the top to 
an inch-wide glass tube, in order to allow the traversing 
of the top of the glycerine column to be observed. 
The cistern was a glass reservoir, 100 times larger than 
the tube, and was placed at the bottom of the staircase, 
with a layer of paraffin floating upon the top of the 
glycerine to prevent it from absorbing moisture from 
damp air. The top of the column, and the graduated 
scale for noting the rise and fall of the column of 
glycerine, were placed on the landing-stage at the top 
of the staircase. A change in the condition of air 
which made a difference of i inch in the height of the 
mercurial column of a barometer, made a difference 
of 10 inches in the height of the glycerine. The 
barometer was. therefore, more sensitive than an ordi- 

1 6 Meteorological Lechires. 

nary mercurial one, to this extent. The specific gravity 
of glycerine is V2J. 

A pump can only suck water up 34 feet out of a 
well, because a column of water 34 feet long weighs 
the same as a column of the atmosphere of a like 
transverse area. When the pressure is lifted off the 
top of the pipe by the raising of the piston, the 
atmosphere resting upon the surface of the water in 
the well squeezes the liquid up into the pipe ; but it 
can only do so until the weight of the water-column, 
which it has driven up into the pipe, is equal to its own 
pressure. A pump is, in a certain sense, a water- 
barometer. The water can be sucked up higher by a 
pump when the atmospheric pressure upon the well is 
high, than it can be when it is comparatively low. 

9. Pressvire of Air in all Directions. 

The atmosphere not only presses down towards the 
earth by its weight. It also presses with equal force in 
all directions around when it is squeezed down from 
above. This, again, is one of the constant conditions 
of fluid pressure. It is due to the ready and free 
mobility of the atoms of fluids and of liquids amongst 
themselves. The pressure which acts in the downward 
direction is also transferred through the freely moving 
particles towards the side. The Magdeburg hemi- 
spheres are, for this reason, pressed together laterally 
when the air is pumped away from between them. A 
plate of flat glass is held firmly pressed up against the 
bottom of a glass cylinder if pressed down by it into a 

The Physical Pi'opcrties of the Atmosphere, i 7 

vessel of water. From this cause all bodies weigh less 
in air than they would do in empty space. They are 
sustained, to some small extent, by the upward pres- 
sure of the fluid air which they displace. A sphere of 
any kind, with a volume of 12 cubic inches, loses 3-1 
grains of weight in air, because that is the weight of 
the 1 2 cubic inches of air which it displaces. 

The most important circumstance in reference to 
this pressure of air in all directions around is, however, 
that it becomes the effective cause of the production of 
air movement or wind. When a heavy column of air 
presses down by the side of a lighter one, the air sub- 
stance which lies beneath is always squeezed away from 
the place where the pressure is greatest towards that 
where the pressure is least. As cold air, of necessity, is 
heavier, bulk for bulk, than warm, there is thus always 
movement of air, or wind, from cold regions of the 
atmosphere towards those which are warmer and 

10. The Chemical Constitution of the Air. 

The air is not, however, a simple gas. It is a 
mixture of several different kinds of gaseous substance 
mingled loosely together. 

The chief bulk of air is formed of two distinct 
gases, which are called oxygen and nitrogen. These 
are merely mixed loosely and mechanically in the 
proportions of 21 volumes of oxygen to 79 volumes 
of nitrogen. The atoms of the two gases float freely 
amidst each other, and it is a curious but well-ascer- 


1 8 MeteoJ'ological Lectures. 

tained fact that they do this with an almost entire 
freedom from any mutual constraint or interference. 
The atoms of the oxygen do not even press by their 
weight upon the atoms of nitrogen. They are quite 
indifferent to their presence, and move in the intervals 
between them as if they were moving in space, void of 
everything but themselves. This is an essential con- 
dition of gaseous existence. All kinds of gases be- 
have themselves in this way. One kind of gas dif- 
fuses itself freely through the interspaces that lie be- 
tween the atoms of another kind without suffering 
any obstruction from their presence beyond a very 
trifling retardation of their movements. The oxygen 
and nitrogen, under the influence of this gaseous dif- 
fusion, are evenly distributed through all parts of the 
atmosphere. There is the same relative quantity of 
each of these constituents everywhere. 

11. The Aqueous Vapour of the Atmosphere. 

Vapour always rises up into the air from water. 
Minute molecules of the water ascend into the air, and 
float freely about in a quite invisible state in the 
interspaces between the atoms of the oxygen and nitro- 
gen. They are invisible because they are very minute 
in themselves, and because they are many of their own 
diameters asunder. The vapour state is thus physi- 
cally very analogous to that of a gas. The only differ- 
ence between a vapour and a gas is, that the vapour 
can change its state at natural temperatures from the 
liquid to the invisible gas-like form, and from the gas- 

The Physical P7'opertics of the Atmosphere. 19 

like condition back to the state of liquid ; whilst the 
gas under the same circumstances remains permanently 
in the thinly spread out and invisible condition. Liquid 
water is readily turned into thin and quite invisible 
vapour, and thin invisible aqueous vapour is quite as 
easily turned back into visible liquid. 

But only a certain definite quantity of the mole- 
cules of water, spread thinly out in this quasi-gaseous 
or vaporous form, can be received into the interspaces 
of the air-atoms in this way. As soon as that quan- 
tity is reached the invisible and transparent state of 
the vapour ceases to be maintained, and the molecules 
begin to aggregate together so as to present them- 
selves to the eye as visible mist. In other words, the 
vapour begins to be deposited as water, and to fall 
through the air. Whenever it happens that the inter- 
spaces of air hold the full charge of vapour which it is 
capable of sustaining in the invisible state, such air is 
said to be saturated with invisible moisture. 

Warm air, however, is not so easily saturated with 
moisture as cold. The warmer the air is the larger the 
quantity of invisible vapour that it can sustain stored 
away in the interspaces that lie between its atoms. 
Thus, air at the temperature of 32° Fahrenheit can 
sustain the x^gth part of its own weight of transpa- 
rent vapour ; at the temperature of 5 9° the -g^yth part 
of its weight ; and at 86° as much as the ^^th part 
of its weight. In other words, for every addition of 27° 
of temperature the capacity of air to sustain invisible 
vapour is doubled. 

20 Meteorological Lectures. 

The height of the column of the barometer gives 
the combined weight of the oxygen and nitrogen gases 
of the air, and of the aqueous vapour ; that is to say, 
each one of these constituents produces an effect in 
lifting the column of the barometer. 

Fully saturated air at a temperature of 32*^ Fahren- 
heit contains only 2'37 grains of aqueous vapour in each 
cubic foot. Saturated air at a temperature of 60° con- 
tains 5 '8 7 grains in each cubic foot ; and saturated air 
at 80°, iO'8i grains. If, therefore, at any time fully 
saturated air, with a temperature of 80°, is suddenly 
chilled to 60°, very nearly 5 grains of water arc thrown 
down out of each cubic foot. Such really is the 
effective cause of rain. Warm air drinks up as much 
invisible vapour as it can hold, floats it away on the 
wings of the wind, and then, when it reaches some 
colder place, throws a considerable portion of it down 
in actual droplets of water. 

Evaporation of water into the air is increased, it is 
to be understood, to some slight extent by low atmo- 
spheric pressures, and is also favoured by wind, which 
sweeps the vapour away as it rises. So again, on the 
other hand, the production of air movement, or wind, 
is in some sense facilitated by the mechanical influence 
of rising vapour. 

12. The Cooling Effect of Evaporation. 

Each grain of water, when it is turned into vapour, 
carries off with it sufficient heat to raise 960 grains 
of water 1° Fahrenheit. That much heat is conse- 

The Physical Properties of the Atmosphere. 1 1 

quently taken away from the water. The water from 
which the vapour ascends is cooled to that extent. 
The heat, however, is not lost. It is merely absorbed 
into the vapour, and retained there in a latent or sleep- 
ing state ; that is, in a state in which it is no longer 
capable of producing an effect upon the thermometer, 
or of exciting the sensation of warmth. It is em- 
ployed, whilst retained in that latent state, in maintain- 
ing the thin and expanded condition of the vapour ; 
in keeping its molecules floating loosely and widely 
apart, instead of in producing the sensation of warmth. 
The whole heat, however, is given back to the air in a 
sensible state, when the vapour is again condensed into 
water. This is one reason why the occurrence of rain 
is so frequently accompanied by an elevation of the air 

13. The Cooling Effect of Rarefaction. 

In ascending into the higher regions of the atmo- 
sphere, as in climbing a lofty mountain, it is found 
that the air continually gets colder and colder with the 
ascent. This is due to two influences. First, the 
higher the region, the farther it is removed from the 
warm ground, which is the principal source of the heat 
communicated to the air. The sun's warmth is given 
first, not to the air itself but to the solid ground, and 
the air is then warmed by touching the ground, and by 
floating away with the heat which it receives. But 
over and beyond this, as the air expands under the 
diminution of pressure in the higher regions, it absorbs 

22 Mcteoi^ological Lectures. 

sensible heat to maintain the expansion of its own 
substance, and renders that latent and insensible. The 
air itself thus becomes cold in consequence of its 
warmth being taken away from it for use in a different 
way. Heat is always absorbed and rendered insensible 
during the rarefaction of a gas ; and is invariably 
developed and made sensible during its condensation. 
Enough heat can be produced to set fire to a piece of 
tinder by squeezing air suddenly down in the inside of 
a closed syringe. 

The outermost limit of the atmosphere gets cooled 
down by rarefaction probably to —JjV Fahrenheit 
over the equator ; and to —I 19?,' over the poles. 

14. Diathermancy of Dry Air. 

The solar rays pass through pure dry air without 
warming its substance at all. The air is, so to speak, 
transparent to heat. That peculiar property is termed 
diathermancy.^ Professor Tyndall has shown, by direct 
experiment, that dry air, and indeed the gases nitrogen, 
oxygen, and hydrogen are as freely permeable to heat 
as a vacuum or empty space. 

15. Heat-absorbing Power of Aqueous Vapour. 

Aqueous vapour, even when in its most invisible 
and transparent state, on the other hand, acts as a 
powerful screen to the heat rays of the sun, arresting 
them in itself, and preventing them from passing freely 
on. This is a very important fact. The aqueous 

1 From otd, through, and depfJ-V, heat. 

The Physical Properties of the Atvwsphere. 23 

vapour of the atmosphere not only stops a good part of 
the sun's warmth before it reaches the earth, but also 
further acts in keeping the warmth there when it has 
once struggled through as far. Professor Tyndall has * 
shown that i o per cent of the warmth which is radiated 
back from the solid surface of the earth, through moist 
air, is arrested within lo feet of that surface. The 
sunshine on mountain tops scorches very severely, 
because the air above them is too dry to afford any 
screen from the heat. But the heat of low-lying places, 
even in the tropics, is not scorching, but soft, because 
there its greatest force is intercepted by the abundant 
vapour that is sustained in the lower strata of the air. 

Professor Tyndall thinks that the rain deluges 
which often fall in tropical calms are partly due to the 
powerful radiation of the heat through the dry air 
which rests above the lower region of great moisture. 
He conceives that the ascending column of fully-satu- 
rated air expends its heat by free radiation when it gets 
above the dense vapour-screen of the lower elevation, 
and that the superfluous vapour is then condensed 
by the chill, and thrown down as a copious torrent 
of rain. The formation of cumulus clouds may be 
ascribed to a similar cause. The visible vapour 
is formed where the radiation goes on most vigor- 
ously through the rare dry air above. Professor 
Tyndall very expressively speaks of the cumulus 
cloud as the capital of an invisible column of satu- 
rated air. Mountain tops gather clouds around them 
for the same reason ; they cool themselves by radiat- 

2 4 ]\Ietcorologica I L cdu res. 

ing their heat, through the dry superincumbent air, 
into space ; they also, of course, increase this effect 
by deflecting moist winds up towards their summits, 
* and by causing them to expand and deposit their 
moisture, as they rise, under the diminution of pressure. 
Even over the torrid desert of the Sahara the nights 
are comparatively cold, and the daily range of tempera- 
ture is large, because the air is there exceedingly dry 
and clear, so as to permit very powerful radiation at 

It must hence be understood that a clear, cloudless, 
starlit sky, is not necessarily a good medium for the 
radiation of terrestrial heat. For that purpose its air 
must be dry as well as clear. A moist clear air acts 
effectually as a heat screen. 

16. The Carbonic Acid and Ammonia of the 

Two other gaseous substances are found constantly 
present in the interspaces of the air-atoms, mingling 
their molecules with those of the aqueous vapour, 
although in very much smaller proportional amount. 
These are the compound gases which are known as 
carbonic acid and ammonia, and which are poured 
continually into the atmosphere by the decomposition 
and combustion of organised structures. Their quan- 
tity is, indeed, so small that no account is taken of 
their presence by the barometer. The proportion of 
the pressure which they produce is so slight that it is 
overlooked in barometric results. There are about "^"^6 

The Physical Properties of the Atmosphere. 25 

■gallons of carbonic in every 10,000 gallons of air, and 
a trifle more than the same quantity of ammonia in 
10,000,000 gallons of air. Small as these proportional 
quantities are in themselves, they are, nevertheless, 
capable of yielding very considerable supplies when 
large spaces of the atmosphere are concerned. The 
air which rests upon i square mile of land at any in- 
stant, contains in itself not less than 1,300,000 tons of 
carbonic acid, and therefore as much as 371,475 tons 
of the solid element carbon, converted to the gaseous 
state by its combination with oxygen. The rain carries 
down, every year, to each acre of ground, 30 lbs. of 
ammonia, although, on account of its great solubility, 
this gas is looo times less abundant in air at any one 
time than carbonic acid. 

17. The Nature of Ozone. 

A peculiar odour is developed in the atmosphere, 
chiefly through the influence of electrical discharges of 
high intensity, and by the evaporation of water, which 
has been referred to the production in small quantities 
of a distinct substance, which, in consequence of its 
peculiar smell, was named ozone by Professor Schonbein 
of Basle, in 1840.^ It exists in very small propor- 
tional quantities in the atmosphere, even when most 
largely developed. There is rarely more than i gallon 
of ozone in 700,000 gallons of air. 

It is now known, however, that ozone is not a 
distinct substance, but merely a condensed and excep- 

^ From oj'o), I (have a) smell. 

26 Meteorological Lcchires. 

tionally active condition of oxygen. Dr. Andrews 
succeeded in demonstrating, by direct experiments in 
1856/ that ozone is simply oxygen condensed to the 
extent of one-half of its volume, and that it can be 
turned back into oxygen by exposing it to high tem- 
peratures. Ozone is distinguished by its very high 
oxidising i^owers. It destroys the mobility and bright 
lustre of metallic mercury, removes potassium from its 
neutral combination with iodine, thus leaving the latter 
element free to produce its characteristic blue colour 
with starch, and it rapidly decomposes most organic 
substances. In densely peopled towns there is, on this 
account, an entire deficienc}' of ozone in the air ; but 
it is generally present in full quantity in the air of 
open country districts, and still more especially in the 
neighbourhood of the sea. 

18. The Transparency of the Atmosphere. 

Pure air is freely permeable to the \-ibrations of 
light ; they pass through amidst the atmospheric 
atoms v^ery nearly as freely as they would through 
blank space. The diathermancy and transparency of 
the atmosphere, it may be remarked, are of the very 
highest importance to the existence of living creatures 
upon the earth. In consequence of the diathermancy 
of the atmosphere the heating power of the sunshine 
penetrates down to the terrestrial surface to produce 
the various molecular activities and changes upon 
which vital operations depend. The transparency of 

1 See Philosophical Transactions 0/ the Royal Society for 1856. 

The Physical Properties of the Atmosphere. 27 

the air opens the window of the earth, so to speak,, 
first for man's outlook into the surrounding regions of 
space, and secondly for the admission of those wonder- 
ful effects of light which render terrestrial objects 
visible, and which clothe their surfaces with beautiful 
diversities of colour, and of brilliancy and shade. It 
only needs that London should be thought of as it 
exists in a dense November fog, for a very vivid idea 
to be presented to the mind of what the earth would 
be without the diathermancy and transparency of its 
atmospheric investment. It is a noteworthy fact that 
aqueous vapour in its most elastic state does not arrest 
the luminous vibrations as it does the vibrations of 
heat. It is as transparent to light as pure air itself 

As soon, however, as aqueous vapour begins to be 
condensed into visible mist its permeability, by the 
vibrations of light, is destroyed. The gorgeous colours 
which appear over the western horizon after sunset are 
due to even the strongest vibrations of light, — those, 
namely, which produce the impressions of yellow, and 
orange, and red, — not being able to penetrate freely 
through those portions of the atmosphere which are 
then more or less laden with mists and clouds. The 
yellow and red vibrations are caught by the gathering 
mists and turned back to the surface of the earth, and 
to the eyes of observers there placed. Even in its 
purest state the atmosphere appears to be not quite as 
freely permeable to the vibrations of light as it is to 
those of heat. The blueness of the so-called sky is in 
reality due to the faint blue vibrations reflected up from 

28 Meteorological Lectures. 

the earth being caught by the air-particles and vapour- 
molecules which are crowded up behind each other 
for mile after mile in the atmosphere. The atmosphere 
is blue overhead, because it is able there to arrest and 
turn back to the eye the blue vibrations of light which 
are struggling out through it towards external space. 
Air is a blue medium really when the vast depth of 
the atmosphere is taken into account, instead of being 
absolutely colourless and absolutely clear. In ascend- 
ing to the higher regions of the atmosphere the sky 
continually assumes a deeper and darker blue, because 
with each additional stage of ascent there remains 
less air-substance above to arrest and turn back the 
blue vibrations. 



The subject on which I have the honour to address 
you this evening is one that may perhaps be considered 
as trespassing somewhat on the domain of geography. 
I will not admit the trespass ; but I will readily admit 
that not only this, but a great deal of meteorology, 
is very closely related to that branch of geography 
which seeks, by reference to Physical Science, to illus- 
trate or interpret the facts observed in different parts 
of the world. I should be sorry, indeed, to think that 
meteorology was limited to reading .off thermometers, 
or making other exact measurements ; just as I should 
be sorry to think geography was nothing more than 
exploring, surveying, or map-drawing. If geography 
is to be understood as the study of the earth and all 
that belongs to it, it embraces meteorology, which is 
the study of the superincumbent air — that air which we 
breathe and in which we live. But in any case, the 
two sciences, if not united, are so connected, as to be 
at many points inseparable. Of these, the study of 
climate is certainly one ; for if anything happens to 
make us personally interested in any place, the very 
first questions we ask concerning it are as to the 

30 jMdeorological Lectures. 

climate. To the half-intending settler these are every- 
thing : — Is it healthy? is it wet ? is it dry? is it hot ? is 
it cold ? — these are the questions which principally fix 
his purpose. There are, doubtless, many other points 
which have their own weight : good harbours, a ready 
market, a teeming soil, luscious fruits, heavy grain 
crops, succulent grasses : but though even these are 
but another way of stating some of the conditions of 
climate — rain, sunshine, or tempest — though they have 
thus a direct meteorological bearing, they are still, by 
themselves, not those to which a man trusts, I do not 
say his own life, but the lives of those most dear to 
him ; and they fade into insignificance before that most 
vital of all questions — Is the place fit to live in ? 
The answer involves a special examination into the 
nature of the air ; and though this may, in some 
respects, require instruments more sensitive than man 
can 5'et make — may require, for instance, the delicate 
organisation of man's own body to detect the subtle 
miasma which gives ague or low fever ; in others, 
again, it can be made with almost mathematical pre- 
cision, and the peculiarities of the climate portrayed 
as on a map. Amongst these peculiarities, capable of 
investigation, and falling distinctly within the scope of 
meteorological science, one of the most important is 
the temperature. But it is not only in regulating the 
more serious affairs of life that questions of tempera- 
ture come before us ; they crop up continually ; they 
belong to the bath-room or the greenhouse ; I have 
heard them mentioned in the theatre or the ball-room ; 

Air Tempei'atitre : its Distribution cf Range. 31 

and the street stalls, selling halfpenny ices, appeal to 
a taste which clearly requires no cultivation. Thus, 
then, economically or socially, temperature has an in- 
terest for us which begins at our birth and ends only 
at our death ; and it is perhaps on this account, almost 
as much as on account of its importance as a factor in 
other atmospheric conditions, and as related to changes 
of weather — wind and rain — that the Council of the 
Meteorological Society has placed it first on the list of 
the special subjects included in these Lectures. 

Of the different sources of heat, and of the several 
modifications which heat, when once excited, can un- 
dergo, it does not fall to me to speak. So far as 
climate is concerned, all heat emanates directly or 
indirectly from the sun. If the sun were extinguished 
we should have no heat at all. It is difficult to con- 
ceive such a state of things. Absolute zero, the tem- 
perature at which air is supposed to lose all its elastic 
force, has been estimated as about 500° of Fahren- 
heit's scale below the freezing point of water ; as 
far below it, that is, as the temperature of melting 
lead is above it. But whether the so-called absolute 
zero is any measure of the absence of all heat is, and 
so far as we can see must remain, unknown. It may 
possibly represent the temperature of interstellar space. 
Some writers have supposed that it does ; others have 
supposed space to be very much colder ; others, again 
have conceived that, warmed by distant stars, it is not 
nearly so cold, and have estimated it at about 270° 

32 Meteorological Lectures. 

below freezing point. All this, however it may be veiled, 
is .mere guess-work. The only limit, based on trust- 
worthy experiment, is the absolute zero ; and failing 
any more definite interpretation, I should be inclined 
to accept soo'' below freezing point as a rough 
approximation to the temperature of space. 

The earth itself has often been spoken of as a 
soured of heat ; for it is very certainly known that in 
deep borings the temperature increases at a rate which 
may be estimated as about i° in every 55 feet. But 
this purely terrestrial heat is no longer sensible at the 
surface of the earth, and has nothing whatever to do 
with climate. Climatic heat comes solely from the sun, 
and without the sun we should have everywhere a 
temperature if not of absolute zero, at least far below 
any of which we have a natural experience ; far below 
any ever observed either in Siberia or in the high 
northern latitudes beyond Smith Sound. 

Since, then, the sun is the source of all climatic 
heat, it would seem at first sight as if all places on the 
same parallels of latitude ought to have the same tem- 
perature ; as if the decrease from the equator towards 
the poles should be regular, and everywhere the same. 
That this is not the case is well known to you all ; is a 
matter of familiar personal experience ; for the fact is 
that the temperature of different regions on the face of 
the earth depends on a great many conditions, of which 
latitude is undoubtedly one ; but except over extreme 
distances, by no means a very important one. 

If we mark on a map the mean temperature of as 

Ai7' Temperature : its Disti-ibution & Range. 


many places as possible, either for a month, or a season, 
or a year, and join all those which have the same 
temperature, the lines so drawn are called isotherms 
— lines of equal heat ; and the maps on which they 
are drawn are called isothermal maps. The suspended 
map shows, in different colours, the isotherms for 
January, for July, and for the year ; and you will see 
almost at a glance how widel}', how irregularly, they 
differ from the parallels of latitude. It is evidently 
quite impossible to say that any particular temperature 
belongs to any particular latitude at any particular 
season ; it is quite impossible to calculate from the 
position of the sun and the latitude w^hat the tempera- 
ture at any place ought to be ; though this was long a 
favourite idea. All that we can do is by actually 
observing a great number of temperatures at different 
places on any one parallel, and taking the mean of 
them, to form, from that, some idea of the temperature 
belonging to that parallel. The mean temperature so 
found has been called the normal temperature of the 
latitude ; and the temperatures which differ from that 
mean are abnormal. If we mark on a map, at a number 
of places, the extent of the difference from the normal, 
and join those in the same neighbourhood that have the 
same difference, the lines so drawn are called isabnor- 
mals, and the map becomes like these now before you ; 
where the blue colour shows the parts below the normal 
temperature, and the brown those that are above it. 
Such maps are interesting, as showing, from a different 
point of view, the very slight connection between 

34 Meteo7'ological Lcctujrs. 

latitude and mean temperature ; but beyond that they 
have but little signification, and the normal referred to 
is altogether artificial. 

What, then, is the reason of this very marked 
irregularity ? Of mere local causes, the most important 
is what we commonly know as aspect. A place front- 
ing towards the mid-day sun, on the side of a slope, 
sheltered from cold winds by a line of hills or high land, 
or even a clump of trees, is often found to be very 
much warmer than other places, in the same neighbour- 
hood, but less favourably situated. Many of our south 
coast watering-places are familiar examples of this: 
Ventnor and Torquay to an almost extreme degree. 
As far as mere sensation goes, between the Undercliff 
on a fine July afternoon, and Queen's Road at Hong 
Kong, I don't know that there is much choice. Aber- 
dour, on the south coast of Fife, is another somewhat 
similar locality, where, sheltered and warmed by a low 
cliff, geraniums and veronicas may be seen in full 
flower at Christmas or the New-Year. The same cause 
acts of course in every part of the world. As compared 
with neighbouring localities, the temperature of any 
place depends almost entirely on its aspect and shelter. 
Examples of this will occur to every one; but, as a very 
marked instance of the force of mere aspect under the 
most difficult circumstances, I may refer you to Sir 
George Nares's notice of a little lake near the "Alert's" 
winter-quarters, which, though 500 feet above the sea, 
showed no sign of freezing, when the temperature at 

Air Teinperatiwe : its Dist7'ibntion &• Range. 2,^ 

the sea level had fallen to 28°, and no water was to be 
got on the lowlands.^ 

This reference to Arctic observation reminds me of 
another and rather curious cause of local differences of 
temperature. When water is turned into ice a great 
deal of its contained heat is — so to speak — squeezed 
out of it ; its molecular energy is transferred to the sur- 
rounding air, and is dispersed. But when this is done 
on a large scale, it may and does produce a marked 
and apparently paradoxical increase of temperature, 
and for the moment soften the rigour of an arctic 
climate ; an effect which has been more especially 
noticed in Siberia, as accompanying the freezing of the 
sea, and the lakes, and the rivers, in October." Thaw- 
ing acts in exactly the opposite way ; for ice, as it is 
converted into water, absorbs a great deal of the sur- 
rounding heat, and lowers, or tends to lower, the general 
temperature. It is thus that, within the Arctic, those 
localities which, by the configuration of the land and the 
set of the tides or currents, are permanent ice-traps, 
have an exceptionally severe climate. Melville Bay 
may be named as one of these. Rensselaer Bay — 
Kane's quarters for two miserable winters — is another; 
whilst Port Foulke, between the two, is described as 
mild in comparison. The difference is to be attributed 
not to the mere presence or absence of ice, but princi- 
pally, perhaps, to the fact that ice formed in the one 

^ Voyage to the Polar Sea, vol. ii. p. 142. 

^ Wrangel's Expedition to the Polar Sea, p. 48 (2d edition, by 
Col. Sabine). 

36 Meteorological Lecttwes. 

place where it gave out its heat, and floated away to 
thaw and absorb heat in the other. 

When from smaller, or, as they may be called, more 
purely local causes, we pass on to larger or geographical, 
the most patent are the dififerences of soil, or geological 
conformation. The sun shining on the air does not heat 
it to any perceptible degree ; the direct heat of the 
sun passes through air, as its light passes through glass ; 
but when it warms the surface of the earth then the 
air is warmed by actual contact, by convection, or radia- 
tion. This may perhaps be a new idea to some of you. 
If the heat, as it radiates from the sun to the earth does 
not warm the air, why should it warm the air either by 
contact with the ground or as it radiates from the 
ground } It is that the character of the heat is 
changed ; that its waves, which were short and quick in 
their vibrations, are now long and sluggish. Heat, 
radiating from an obscure source, is stopped by air, and 
more especially by damp air, in much the same way 
that obscure heat-rays are stopped by a glass screen 
placed in front of the fire. Another familiar illustra- 
tion of the same peculiarity is given by the stifling heat 
of a room when the sun shines full on its closed window ; 
and still more by the heat of a conservatory : the lumi- 
nous heat-rays pass in through the glass ; the obscure 
heat-rays cannot pass out ; the room, or the conserva- 
tory is thus a very heat trap. The heat of the sun can 
in this way be collected to an extent that seems almost 
incredible. If a box, lined with some dark-coloured non- 
conductin": substance — as for instance, with black silk 

Air TempcrattLve : its Distribution & Range. 2,7 

quilted with wadding, or with black wool — and the top 
of it closely covered with two or three slabs of clear 
plate glass, be placed facing an English July sun, the 
temperature will rise far above that of boiling water; a 
small vessel of water placed in it will boil briskly ; but 
the difficulty of carrying off the steam has (I believe) 
prevented this way of catching heat being turned to 
any economical use. Such boxes have been, and still 
sometimes are fitted up, with the idea that the observed 
temperature inside them is a measure of the intensity 
of the sun's rays. The idea is quite a mistake. Very 
high temperatures are often observed in them, but they 
are a measure of nothing at all, unless indeed it be of 
the security of a useless trap. 

Now it is just in this way that when the sun, 
shining through the air, strikes on ground easily 
warmed— that is, with small capacity for heat — such 
ground communicates the heat to the air both by con- 
tact and by radiation ; the heat is obscure, and cannot 
pass freely through. But when, on the other hand, the 
ground is such as is not easily warmed, has — that is to 
say — a large capacity for heat, it holds to what falls 
on it ; and, in some way, converts it to energy within 
itself, and the surrounding air receives but little. Of 
this nature are lands covered with grass or other vege- 
tation ; and, to a still greater degree, the snow-clad 
plains of high latitudes, or the slopes of lofty moun- 
tains. One of the many marvels told by Arctic 
travellers is of the intense heat of the sun blistering 
black paint, or making the pitch boil and bubble up 

38 Meteorological Lectures. 

from the seams of the ship's deck, whilst the snow is 
lying thick all around, and the air in the shade has a 
temperature far below freezing point. On the high 
Alps, or on the Himalayas, similar experiences have 
been recorded. Professor Tyndall has told us that 
above the grand plateau of Mont Blanc, he has felt the 
heat of the sun well-nigh intolerable, although at the 
time hip-deep in snow ; and Sir Joseph Hooker, 
amongst other curious obser\'ations in the Himalayas, 
saw, one December morning, at a height of 1 0,000 
feet, the mercury, in a black bulb thermometer exposed 
to the sun's rays, mount to 132°, whilst the temperature 
of shaded snow hard by was 22°. Such heat of course 
falls on the snow ; but a great deal of it is at once 
reflected, and what is not is absorbed by the snow ; 
possibly in liquefying some little, which is shortly after- 
wards again frozen, and the heat dispersed. 

Very different is the action of the sun's heat when 
it falls on sandy or stony ground, which is easily 
warmed and as easily parts with its warmth. The 
resulting effect of this is very familiarly known ; and the 
extreme mid-day heat of the great deserts, whether in 
Asia, or Africa, or America, or Australia, as compared 
with that of many other places nearer the sun, is but a 
larger and intensified example of the action of the 
same cause that makes us prefer, for a summer walk, 
a country field path to a white macadamised road.. 

The observed temperature, on some occasions, at 
desert stations, is almost incredible. At IMurzuk, an 
oasis of the Sahara, an air temperature of 130"-, and 

Air Temperature : its Distribution & Range. 39 

even a degree or two more, has been noted. At 
Cooper's Creek, a spot rendered classical, in the history 
of Australia, by the deaths of those gallant explorers 
Burke and Wills, a thermometer, which was marked 
up to 127°, burst whilst lying in the sheltered and 
shaded fork of a tree ; how much more than 127° the 
temperature was at the time was undetermined. Many 
similar instances might easily be collected from the 
experiences of travellers in the deserts ; they are by no 
means rare ; but they must nevertheless be considered 
exceptional ; for their domain, however large, is small 
as compared with the area of the globe's surface. 

More important, by far, from a geographical point 
of view, are the prevailing winds of any locality, and 
their relations to the ocean currents in its neighbour- 
hood. Heat or cold may be, and often is, carried into 
a country by wind which has gained or lost warmth in 
passing over burning soil or snow-covered regions. 
The air is indeed the receiver and transmitter of all 
the heat that makes the earth habitable ; without the 
air and the clouds of vapour in it, the heat, as soon as 
it strikes the earth, would be radiated back again into 
space ; it is by the air that it is confined and rendered 
available for the support of life. The air has thus, in 
the economy of Nature, a use almost as important as 
that of oxygenizing our blood. Necessary as the air 
is for us to breathe, it, or some other gas in its stead, 
is equally necessary to warm us. 

But notwithstanding this importance of air, great as 
are the climatic effects of wind, its necessary ally is the 

40 Meteorological Lectures. 

ocean : the effects of wind are mainly due to the ocean 
currents, for though it is by the wind that the warmth 
is carried over the land, it is from the ocean that it 
gets that warmth ; it is by the currents of the ocean 
that the warmth is carried from low to high latitudes ; 
it is by the currents of the ocean that arctic cold is 
carried into the tropics. 

The power of dry air to carry heat is trifling as 
compared with that of the same volume of water. In 
scientific language, water has a much greater capacity 
for heat than air has. The quantity of heat that 
would raise by i° Fahrenheit the temperature of a 
cubic foot of water, would raise b}' i° the temperature 
of 3234 cubic feet of air; or, which amounts to 
the same thing, would raise the temperature of a 
cubic foot of air by 3234°. The water absorbs the 
heat and carries it about wherever it goes ; the air, 
on the other hand, can hold but little, and throws it 
off into space at the first opportunity. Air, in contact 
with a heated soil, may be raised to a high temperature, 
much higher than water is ever raised to by the action 
of the sun : I have already said that the air is occa- 
sionally raised to a temperature of more than 130'^; 
the water of the sea perhaps never exceeds 85° : but the 
water, nevertheless, contains a very much greater amount 
of heat, and can carry it to much greater distances. 
It is by reason of this that ocean currents have the 
enormous climatic effect familiarly attributed to them. 
The Gulf Stream has been so often talked of, that it 
has been voted a nuisance ; it is a nuisance that we 

A h' Temperature : its Dist^dbution & Range, 4 1 

could very ill do without. Its climatic effect, when 
stated in measures of heat, is stupendous — it is the 
very poetry and romance of arithmetic ; and perhaps 
you may think that a thing that can get poetry out of 
the multiplication table is marvellous indeed. 

The heat brought by the Gulf Stream into the 
North Atlantic has been fairly estimated as not less 
than one-fifth of the whole heat possessed by the 
surface-water of that division of the ocean. Now Sir 
John Herschel, and other eminent writers, English and 
French, have estimated the temperature of space at 
239° below zero ; it is, as I have said, probably enough, 
considerably lower. If with this we compare the exist- 
ing temperature of the North Atlantic, which may be 
taken as 56° above zero, we find that the heat which 
it actually has corresponds to a temperature of 295°, 
the fifth part of which is 59°. If then, the fifth part of 
its heat, the heat derived from the Gulf Stream, were 
taken away from it, the surface-water of the North 
Atlantic would have an average temperature of 3° 
below Fahrenheit's zero, or 35° below the freezing 
point of fresh water.^ Such a calculation may appear 
almost wild, but it errs, if anything, in allowing too 
much heat. I am by no means sure that, instead of 
35° below freezing point, I ought not to say nearly 

Another way of considering the effect of the Gulf 
Stream leads to a result scarcely less startling. A 
quantity of water, which may be roughly estimated at 

^ CroU's Climate and Time, p. 35, et seq. 

42 Meteorological Lectures. 

about five billions of cubic feet, is hourly poured 
through the Straits of Florida into the North Atlantic. 
This water has then an average temperature of not less 
than 65°, and after performing a circuit in the North 
Atlantic, returns to the tropics with an average 
temperature of not greater than 40°. It gives out to 
the air of the North Atlantic the heat corresponding 
to a difference in temperature of 25°. Now, if you will 
remember that our standard measure of heat — the 
British thermal unit — is the quantity of heat necessary 
to raise the temperature of i lb. of water by 1°, and that 
a cubic foot of water weighs about 64 lbs., you will 
see that the heat so thrown out every hour into the 
airof the North Atlantic is 25 x 64 x 5,000,000,000,000 
thermal units. 

Such a row of figures conveys little meaning ; I 
will try to make it more intelligible. Every thermal 
unit, when converted into power, is capable of lifting a 
weight of 772 lbs. through a height of i foot- — -this 
is the law of equivalence, experimentally established by 
Dr. Joule of Manchester. Consequently, the heat 
hourly dispersed from the water of the Gulf Stream, if 
stored up and applied as power, would be capable of 
lifting, each hour, 772 x 25 x 64 x 5,000,000,000,000 
lbs. through a height of I foot ; that is, of doing the 
work of steam-engines having an aggregate horse- 
power of 3,1 19,000,000,000 — a power equal to that of 
nearly 400,000,000 ships such as our largest ironclads.^ 

Numbers such as these, however vague they are in 

^ Climate and Time, p. 25. 



Ai)' Temperature : its Disti'ibtition & Range. 43 

themselves, and perhaps even by reason of their vague- 
ness, will serve to give you some idea of the enormous 
quantity of heat carried by the Gulf Stream. This 
heat is dispersed into the overlying air, and in it is 
wafted by the south-westerly winds over the north- 
western parts of Europe, and in a very large proportion 
over our own favoured country. It is this that makes 
the astounding difference between the climates on this 
side the Atlantic and on the other; it is this which gives 
us here our green fields and open harbours through the 
winter, when Labrador, and Newfoundland, and New 
Brunswick, in the same or lower latitudes, are buried 
beneath snow, and when the Gulf of St. Lawrence is 
choked with ice. 

But notwithstanding this great difference, a con- 
siderable share of this heat given out by the Gulf 
Stream, is spread abroad over North America, a con- 
siderable share is carried into the Arctic circle ; and their 
climates, however rigorous they actually are, are less so 
than they would be if there was no Gulf Stream. Other 
currents, whether hot or cold, act all over the world in 
a similar manner ; you can trace their effects on the 
isothermal or isabnormal maps before you ; they carry 
away excess of heat from one place, excess of cold from 
another, and everywhere tend to mitigate the extreme 
degree of either. It is difficult to exaggerate their 
importance ; and indeed Mr. Croll, one of the most 
earnest and able exponents of this branch of geography^ 
has summed up his arguments and calculations in the 
incisive sentence, " without ocean currents the globe 

44 Meteorological Lectures. 

would not be habitable." The function of the two 
great oceans — the Atlantic and the Pacific — is, he 
concludes, to remove the heat from the equator, and 
carry it to temperate and polar regions. Aerial 
currents could not do this. They might remove the 
heat from the equator, but they could not carry it to 
the temperate and polar regions ; it would be dissipated 
into stellar space. The ocean alone can convey it to 
distant shores. But aerial currents have, nevertheless, 
a most important function : it is theirs to distribute over 
the land the heat brought, by the ocean currents, into 
the higher latitudes, and on the one, as on the other, 
depends the thermal condition of the globe.^ 

This mutual action of the great currents of air and 
water, their relation one to the other, has not, I think, 
been fully realized, even by some of our most eminent 
writers. Sir John Herschcl himself has said," "The 
effect of land under sunshine is to throw heat into the 
general atmosphere, and so distribute it by the carrying 
power of the latter over the whole earth. Water is 
much less effective in this respect, the heat penetrating 
its depths and being there absorbed ; so that the surface 
never acquires a very elevated temperature, even under 
the equator." In writing thus he clearly overlooked, 
for the moment, the great carrying power of water ; 
overlooked also the very small carrying power of air ; 
but when a man such as Sir John Herschel has made 
this mistake, it is not to be wondered at that others 
have repeated it ; have spoken of wind as the principal 

1 Climate and Time, p. 51. " Outlines of Astronomy, sec. 370. 

Air Tcmpcj'atitre : its Distrihition <2f Range, a^^ 

or only agent in transferring heat from one place to 
another, and have ascribed to hypothetical volumes of 
hot air phenomena which, under the circumstances, 
they could not possibly produce. 

One favourite instance of this is a reference to the 
retrocession of the Swiss glaciers, which were formerly 
of very much greater size, as is proved by the positions 
of the old terminal moraines. It has been urged over 
and over again that this former vast extent was due to 
the fact, that what is now the Sahara was then the bed 
of the sea. Air passing northwards would not then, it 
has been said, carry with it the heat that is now brought 
from the sandy desert. The hot wind which does come 
from the sandy desert, known to all Mediterranean 
travellers as the Scirocco, has many curious and 
disagreeable properties ; but as a set-off, it has been 
supposed to soften the climate of Switzerland, and to 
cause the glaciers to creep back to their present com- 
paratively small size. 

This claim in favour of the Scirocco cannot be 
allowed. Whatever redeeming qualities it may have — 
and I know of none — it certainly has not this : when it 
strikes the shores of Genoa or Provence, it is no longer 
a markedly hot wind, and it has no relation whatever 
to the peculiar hot wind of Switzerland, known locally 
as the Fohn, which, in a careful examination by several 
Swiss meteorologists, and especially by Dr. Wild,^ now 
the Director of the observatory at St. Petersburg, has 
been proved to be an extension of the westerly or 

1 Uebcr Fohn 2t. Eiszeit. Bern, iS68. 

46 Meteorological Lee hires. 

south-westerly winds of the North Atlantic, carrying 
inland the warmth and moisture of the Gulf Stream. 
But the way in which these are converted into the very 
remarkable dry heat of the Fcihn deserves special 

The Fohn, as such, is known only in the north- 
eastern valleys of Switzerland,^ and it is there distin- 
guished by its great heat, and, still more, by its peculiar 
dryness, before which the snow disappears, both by rapid 
melting, and also by that rapid evaporation which has 
obtained for it the appropriate name of the snow-eater 
(Schneefresser). But whilst the Fohn proper is blowing 
in the valleys of the north-east, eating away the snow in 
winter, or in summer and autumn drying the hay and 
ripening the grapes, over the south-west of Switzerland 
a warm and wet wind blows, which precipitates its 
moisture in a heavy down-pour, and floods the country 
with rain and melted snow. The connection between 
these two has been clearly traced only within the last 
few years. When air is driven or lifted to a great 
height, as by being pressed up a mountain slope, the 
expansion of its volume causes a corresponding lowering 
of its temperature, and the air which approaches the 
mountains on the west should experience a certain 
definite loss of temperature whilst being lifted to the 
mountain-tops ; the amount of which may be easily cal- 
culated by a reference to the height of the mountains 
and the diminution of barometric pressure. But if the 

^ The distinctly Fohn stations named by Dr. Wild are Glarus, Auen, 
Altdorf, Engelberg, Schwyz, Chur, and Klosters. 

Ail' Tempei'atttre : its Distribtttion & Range. 47 

air is moist, the chilling, to which it is thus subjected, 
condenses the vapour, causing heavy rain on the wind- 
ward, that is the western, slopes. Now, vapour, when 
turned into water, gives out a great deal of heat ; the 
heat which it has previously absorbed, which gives it 
molecular energy, and which is very commonly known as 
latent heat ; and this heat, set free, warms up the sur- 
rounding air ; so that the temperature at the mountain- 
top may be, and is, many degrees higher than, accord- 
ing to the calculation based on the loss of barometric 
pressure, it ought to be. If now, this air, with the 
moisture squeezed out of it on the mountain-tops, and 
its temperature raised by the heat of condensation, is 
forced down into the valley beyond, the increase of 
pressure, as it goes down, raises the temperature by an 
amount depending, as before, on the height from 
which it has descended, and on the rise of the barometer; 
so that the air comes into the valley with the tempera- 
ture due to the level at which it has arrived, increased 
by the heat conveyed to it, on the mountain-tops, by 
the condensation of the vapour. The air is thus not 
only very hot, but relatively also very dry ; that is to 
say, on the descent of the Fiihn the temperature rises, 
at times, to more than 80°, and the humidity sinks to 
about one-fourth of what the air is capable of holding. 

Of the Swiss Fohn, such as I have described it, 
many here may have personal experience ; but a wind 
similar to it in its peculiar warmth and dryness, is 
observed on the lee side of many mountain ranges. 
Such a wind from the north-west is well known in the 

48 Meteorological Lccttires. 

eastern settlements of New Zealand ; Professor Mohn 
speaks of it as frequent in Norway ; it is not uncommon 
in the Danish stations of Greenland. Three times 
during the February of i860, the temperature at 
Jacobshavn rose through more than 45°, with a south- 
easterly wind; it was observed on board the "P'ox" in her 
celebrated drift down Baffin's Bay in the winter of 1857, 
on the 2 2d of November, when the temperature rose 
through 39°. Even so far north as the winter quarters 
of the "Alert," such a warm south-easterly wind blew 
occasionally ; and once at least, on the 3d of December 
1875, the temperature rose, within a few hours, through 
43°, from 8° below zero to 35° above it, a temperature 
higher than that of any water within 600 miles of the 
ship's position ; whilst at the mast-head, away from the 
cooling influence of the snow, it was found to be some 3° 
higher still. This was at first supposed to be a simple 
warm blast from the south; that it was not so was 
known afterwards by a comparison with the observations 
on board the " Discovery," 46 miles farther south, where 
the wind continued north-westerly, and the temperature 
during the day was never higher than 4° above zero.^ 

In North America, again, the soft wind from the 
Pacific descends on the eastern side of the Rocky 
Mountains hot and dry. It is this that gives the 
peculiar character to much of the scenery of the far 

1 Russell's Climate of Nr,u South Wales, p. 17. Wild's Ueber Eiszeit, 
u.s.'v., p. 56. Nature, vol. xvi. p. 294. M'Clintock's Voyage of the 
"Fox," p. 70. Nares's Polar Sea, vol. i. pp. 203-7; and Moss's Shores of 
the Polar Sea, p. 49. 

Air Teniperattire : its Distj'ibution & Range. 49 

west ; not, as might be supposed, by its climatic effect, 
but by the great fires which it renders possible. The 
wind blowing often for several days in succession, 
greedily drinks up moisture from every source ; the 
pine timber of which houses, barns, fences, etc., are 
built, becomes excessively inflammable ; the weeds and 
grass of the prairies become so much tinder ; and a 
flash of lightning, or a spark from a camp fire, a pipe, 
a gun wad, a passing locomotive, is sufficient to light a 
fire that may spread over a county. It is thus that 
those fires begin which have been familiarly known in 
the great prairie region of the Mississippi, ever since 
its first exjDloration, and which are themselves the 
true cause of the prairies — a distinctive feature of 
North American geography. These have, indeed, been 
commonly attributed to some peculiarity of the soil ; 
but it seems quite certain that, when protected from 
fires, trees flourish there as well as anywhere else ; and 
towards the northern boundary of the prairie region, 
where the limit of this peculiar dryness sways back- 
wards and forwards from year to year, a constant 
struggle is maintained between the two conditions of 
forest and prairie, which gives rise to those beautiful and 
park-like patches of landscape, celebrated as " oak- 

But hot winds of this kind are clearly of a totally 
different nature from those which derive their heat 
directly from the burning soil of a desert, such as the 

^ Prof. Lapham, in Amnial Report of the Chief Signal Office}- to the 
Secretary of War, for the year 1872, pp. 1S6-7. Washington, 1S73. 

50 Meteorological Lectures. 

Scirocco, or the Hot-Wind of Sydney or Melbourne, or 
others experienced in Arabia, Persia, Beluchistan, the 
Punjab, on the West Coast of Africa, or elsewhere; 
winds which may perhaps be explained as the escape 
of air in a state of exceeding tension from an envelope 
of other air rendered viscous by the action of heat.^ 
Some such mode of escape has been well described by 
that able naturalist 'Sir. Thomas Belt, whose early 
death is a loss to almost every branch of physical 
science :" and though Mr, Belt's observations are rather 
of air forcibly expanding upwards through a rent in 
the overlying stratum, I see no reason to doubt that it 
may — under favourable circumstances — expand side- 
wa}-s in a very similar manner. 

In their general effects, cold winds are often still 
more marked than the hot ; even at Sydney, disagree- 
able as the Hot- Wind is, the cold southerly burster that 
follows it is almost as bad : the cold wind that, fre- 
quently during winter, sweeps the continent of North 
America from north to south, is more deadly than any 
hot wind, even than the half-fabulous Samiel or Simoom. 
The snowstorm which such a wind brought over Minne- 
sota in January 1873 — a snowstorm in which some 
300 people lost their lives" — is perhaps one of the most 
memorable of these ; but almost every year similar 
winds blow over Texas and the Southern States ; where 
a fall in the temperature from 70° or 80" to freezing 

^ On this viscosity, see a paper by Mr. Holman in F/iil. .Vag., Feb- 
ruary 1877. - Naturalist in Nicaragua, p. K^fj^et seq. 
3 Times, Feb. 8, 1873. 

A 17' Taiipcratiu'c : its Distrilnitiou & Range. 51 

point, almost within a few minutes, destroys vast 
numbers of cattle, and is occasionally dangerous, if not 
fatal, to men and women. In Cuba, or on the coast of 
Venezuela, the extension of these winds, warmed in 
passing over the sea, is only pleasantly cool ; but in 
South America, a similar cold wind, from the sea be- 
yond Cape Horn, or from the snow-clad passes of the 
Andes, is often felt in Paraguay, and reaches, not un- 
frequently, as far north as the valley of the Amazon ; 
where almost every year there comes a cold spell in 
May or June or July, which lasts sometimes for three 
weeks, and kills not only the nearly naked Indians, 
or the beasts in the forest, but even the fishes in the 

These are some at least of the marked instances of 
these cold winds or cold spells. Others might be easily 
adduced ; and amongst them that regular recurrence of 
cold weather in England every April or May, which 
makes us wonder, and more and more each year as we 
get older, what our forefathers meant when they talked 
of the merry month of May, or of the delights of going 

But besides these principal causes of marked geo- 
graphical or local differences of temperature, there is 
another which affects rather the regularity of temperature 
from hour to hour, from day to night, from summer to 
winter. This is the humidity of the air. It has been 

^ Wallace's Amazon and Rio Negro, p. 43 1 ; Bates's Naturalist on the 
Amazons, vol. ii. p. 224; Chandless, va. Journal of the Royal Geographical 
Society, vol. xxxvi. p. 94. 

5 2 Meteorological Lectures. 

proved, both experimentally and by geographical obser- 
vation, that the heat of the earth radiates with much 
greater ease through dry air than through moist. If 
the air is moist, the heat which passes through it from 
the sun is almost altogether shut in and cannot escape: 
if clouds afterwards cover the face of the sky the effect 
is intensified ; but if, on the contrary, there are no 
clouds, if the sky is clear and the air dry, then radiation 
from the surface of the earth goes on freely, the heat 
passes away into space, and the ground and the air near 
it become sometimes intensely cold as soon as the sun 
sinks below the horizon. 

This change from a hot day to a cold night is often 
well marked in England or the neighbouring countries ; 
in IMay it is frequently most deadly to the young vege- 
tation, or to the buds and blossoms of the fruit-trees. 
A night or two of such frost brings loss or ruin to the 
wine-growers of the south of France, who try — and J 
am told with good success — to prevent the excessive 
chilling by lighting fires of damp litter on the weather 
side of the vineyard, so that the smoke, as a cloud, may 
hang over the tender vines. Our English gardeners get 
a similar protection for their plants by spreading over 
them a net, borne up off the ground by short stakes ; 
and this — almost ridiculous as it seems — is sufficient 
to check the radiation. 

But this alternation from heat to cold is still more 
strongly marked in the great deserts of Africa or Asia, 
where the air is so dry that the radiation is extremely 
rapid, and the differences of temperature are excessive. 

Air Tcmperatiu^e : its DistribiUion & Rajioc^;^ 

This is the peculiar character of what are commonly 
known as continental climates, in contradistinction to 
insular : there is but little vapour in the air, conse- 
quently a scanty rainfall, no heat of condensation set 
free, and radiation unchecked. It is in this way that 
countries in the east of Europe, and in Asia, which 
have a burning heat in summer, experience in winter a 
climate that may fairly be called Arctic. The plains 
of Lombardy, where in summer rice comes to maturity, 
have in winter a temperature as low as that of the north 
of Scotland. The history of our own time has made 
us familiar with the accounts of Crimean heat and 
Crimean cold. In Bulgaria and Asia Minor there are 
the same extremes. With the intense winter cold of 
Khiva, in the latitude of Naples or Lisbon, the story of 
Captain Burnaby's celebrated " Ride " has made every 
one well acquainted, and that in a country which in 
summer is almost impassable from the heat. We have 
all read of the sufferings of the Russian troops in the 
summer campaign of 1873, and how, almost by acci- 
dent, they were saved from utter destruction : on a 
former occasion, 1839-40, they had attempted a winter 
campaign in the same country, but were driven back 
with great loss by the cold, which on several occa- 
sions passed below .the freezing-point of mercury, and 
once fell to 46° below zero. This is equal to the 
rigour of Siberia, and Siberian cold is proverbial, 
although Irkutsk is in the same latitude as Cambridge 
or Northampton, and Yakutsk is little to the north of 
the Shetland Islands. 

54 Meteorological Lectures. 

It is thus very evident that a mere knowledge of 
the mean temperature of a place giv^es little or no idea 
of its climate, or of the forms of life — animal or vege- 
table — for which it is fitted. The mean temperature 
for the year is about the same in the Hebrides and on 
the north shore of the Caspian, or of the Sea of Aral ; 
but there are perhaps no places, between which a com- 
parison can be made at all, where the climate is so 
different. The intense cold of the eastern winter is 
immediately followed by a summer of great brilliancy 
and warmth : there is neither spring nor autumn, unless 
the few days of change may be considered so : corn is 
sown, springs up, ears, and ripens within a few weeks ; 
and choice vines, apricots, peaches, or mulberries, with 
a very moderate amount of care, bear fruit abundantly ; 
whilst in the Hebrides, where snow, seldom lies for 
twenty-four hours, and thick ice is almost unknown, the 
summer is so little better than the winter, that corn 
ripens only in exceptional years, and fruit of any kind 
is an impossibility. 

The climate of the countries bordering on and near 
to the Straits of Magellan is, by the general consent of 
all who have personal experience of it, the most dis- 
agreeable on the face of the earth : " It is so disagree- 
able," says Admiral Fitzroy, " that the country is almost 
uninhabitable. Clouds, wind, and rain are continual in 
their annoyance. Perhaps there are not ten days in 
the year on which rain does not fall, and not thirty on 
which the wind does not blow strongly ; yet the air is 
mild, and the temperature surprisingly uniform through- 

Air Tempcj-atiLi'e : its Dish'ibiitioii & Range. ^^ 

out the year." It is, in fact, uniformly low : it seldom 
falls much below freezing point, but seldom also rises 
much above it. Extremes of cold are unknown ; and 
even with the thermometer at freezing point, the screen 
of vapour mitigates the rigour of the climate. It is 
thus that the vegetable and animal life of Tierra del 
Fuego and of the mainland of Western Patagonia exists 
under such apparently anomalous conditions : dense 
forests on the mountain-slopes stretch upwards to the 
line of perpetual snow ; ferns, of genera closely allied 
to, if not identical with, some of tropical haunts, grow 
freely ; large woody-stemmed trees of fuchsia or ve- 
ronica may be seen, in full flower, within a very short 
distance of the snow-line ; flocks of parrots feed on the 
seeds of Winter's Bark, an evergreen shrub, which they 
perhaps mistake for its Brazilian relatives ; and hum- 
ming birds — despising the rain, snow, and sleet — go 
about merrily, sipping the sweets of the fuchsias, as far 
south as the latitude of 53° or 53-^^^ Farther north, 
the contrasts are almost more apparent ; and in the 
island of Chiloe, in latitude 42°, where the inhabitants are 
frequently compelled to cut their corn before it is ready, 
and bring it into the houses to ripen, the traveller, 
wandering into the forests, might almost fancy himself 
in the Brazils. " Stately trees, of many kinds, with 
smooth and highly-coloured barks, are loaded by para- 
sitical plants of the monocotyledonous structure ; large 
and elegant ferns are numerous; and arborescent grasses 
entwine the trees into one entangled mass, to the height 

' King, \\\ Journal of the Royal Geographical Society, vol. i. p. 1 68. 

56 Meteorological Lectui'cs. 

of 30 or 40 feet above the ground."^. In Tasmania, in 
New Zealand, similar anomalies present themselves : 
tree ferns, which in the northern hemisphere are not 
found beyond the tropic, grow in New Zealand, as far 
south as the latitude of 45° ; and others seem to form 
a connecting link between the very different climates of 
Java and Van Diemen's Land. 

Now these climatic paradoxes may perhaps be, to 
some extent at least, explained by the remarkable 
power of living things to accommodate themselves to 
circumstances ; but the more important lesson which 
they convey seems to be that the distribution of animal 
or vegetable life depends in many cases not so much 
on the mean temperature as on the extremes ; and 
that, while marked extremes, with a wide range and 
a high summer temperature, are favourable to some 
species ; to others, more tender, less capable of enduring 
cold, a small range and extremes of no great compass 
are more suitable. Grape vines would no more bear 
fruit in Fuegia than would humming birds continue to 
chirp on the banks of the Volga, though the mean tem- 
perature at Port Famine and at Astrakhan is about the 

Hence, then, in the study of climate, it is necessary 
to observe not only the highest and the lowest tempera- 
tures, but the mean. As much more knowledge as we 
can get is always desirable, but this much is indispen- 
sable, and calls for careful and accurate observation. 
Our own feelings tell us little or nothing. It is 

^ Darwin, yournal of a Naturalist, p. 271. 

Air Tempei^atiii^e : its Distinbutioii & Range. ^"j 

not only that sudden changes are deceptive. There 
are persons so happily constituted that a cold winter's 
day seems to them mild and pleasant ; there are others 
who would complain of cold on a broiling day in July. 
Other climatic factors also, as well as air temperature, 
affect our sensations : the effects of moisture, dryness, 
calm, or wind, are frequently indistinguishable from 
those of changes of temperature ; or rather, as far as 
we are personally concerned, they are absolutely the 
same. Every one knows how wine may be cooled by 
wrapping the bottle up in wet flannel and hanging it in 
a draught ; the hotter the day, the cooler will often be 
the wine. What do you think would be the effect of 
treating a man or boy in that way 'i It would probably 
kill him. Any of you who have been in India will 
remember very well the unpleasant consequences of the 
punkah-coolie going to sleep ; and yet so far as it pro- 
duces any change at all in the temperature, the real 
effect of the punkah, by churning up the air, must be 
to warm it. I have myself a very lively recollection of 
an evening at Hong Kong, when everybody was gasp- 
ing for breath, declaring that it was hotter than man 
had ever before known it. To corroborate his words, 
some one went to look at the thermometer ; it stood 
at 85°. I have often felt the heat less oppressive 
with the thermometer 15° or 20° higher. Again, the 
recorded experiences of numberless Arctic travellers show 
that Arctic cold may often be pleasant enough. This 
is one of the latest, as given by Dr. Moss, in that gor- 
geous picture-book which has been lately published : — 

58 Meteorological Lectures. 

"In comfortable winter-quarters, and with plenty of 
dry clothing, we found the extremest cold rather curious 
and interesting than painful or dangerous. An icy tub, 
on an English winter morning, feels colder to the skin 
than the calm Arctic air. Cold alone never interrupted 
daily exercise ; it was possible to walk for two or three 
hours over our snow-clad hills, in a temperature of 
100° below freezing, without getting a single frost-bite, 
or perceptibly lowering the- temperature of the body. 
It is possible even to perspire if one works hard enough. 
Our experience led us to think that men, thoroughly 
prepared, might safely encounter far lower tempera- 
tures. Many a time, as we sat round the stove on the 
main deck, discussing the e\'ents of the day and the 
state of the weather, the relative merits of Arctic cold 
and tropical heat were warmly canvassed. Several of 
both our officers and men had lately returned from the 
Ashantee campaign, and they could speak with author- 
ity. There was one thing clear, one could sometimes 
get warm in the Arctic, but never get cool on the 
Coast." ^ 

Such experiences as these are simple illustrations 
of what I mean when I say that, in order to institute 
a strict comparison between temperatures, whether in 
the same place at different times, or in different places, 
and under many different circumstances, exact measure- 
ment and observation are necessary. Without these, 
any record of climate is capricious and uncertain. 

Now, I may assume that every one here knows 

^ Shores of the Polar Sea, p. 47. 

Air Temperature : its Distribtition & Range, ^c) 

that temperature is observed and measured by means 
of an instrument called a thermometer, and knows also, 
in a general way, what a thermometer is. But there 
are thermometers and thermometers ; and between the 
rough instrument of every-day life, such as is hung up 
in a bath-room or a hot-house, and the delicate instru- 
ment used for accurate observations, there is a v^er}- 
wide difference, the extent of which may be roughly, 
though very inadequately, estimated by the difference of 
price: a common bath-room thermometer may be bought 
for a shilling or eighteenpence ; a good standard thermo- 
meter, simple as it seems, and without ornament of any 
kind, but solely on account of the care and skill ex- 
pended on ensuring its accuracy, will cost from two to 
three pounds. 

But given the thermometer, the important question 
is what to do with it .-' How or when is it to be 
observed ? Where is it to be put .'' For of course every 
one knows that the thermometer has different readings 
at different times of the day ; and that its reading even 
at any one time depends very much on where it is 
placed. But though every one knows this, every one 
does not act accordingly; and I have seen thermometers, 
which were supposed to give their owner some idea of 
the temperature, fixed in very remarkable places. The 
drawing-room mantelpiece, with or without a fire 
underneath it, is by no means an uncommon place to 
see a thermometer ; I know, at the present time, of 
one fixed outside a dining-room window fronting the 
south-east, where it receives the direct heat of the sun 

6o Meteorological Lcciuj'es. 

for several hours every forenoon, and the heat absorbed 
by the neighbouring bricks for the rest of the day. 
And putting such extreme instances on one side, a 
great many people are apt to forget the necessity of 
care in placing a thermometer so as to allow it to 
register the temperature of the atmosphere at the time 

It is now definitely concluded that the true temper- 
ature of the atmosphere is its temperature in the shade: 
the heat of the sun's rays is a different thing altogether. 
Now shade, to be perfect, ought to shelter the thermo- 
meter from all disturbing influences ; not only from 
the direct heat of the sun, but from the radiation of 
bodies warmed by the sun, or from radiation to colder 
bodies or into space, from rain, and the consequent 
chilling by evaporation ; the temperature which we 
want to record is that of the air ; and, as far as pos- 
sible, all the surroundings of the thermometer should 
have that same temperature. 

There are, however, many practical difficulties in 
the way of obtaining that ideal condition ; and many 
different ways of overcoming them have been tried, but 
none perhaps with perfect, or at least with undoubted, 
success. Many different stands for thermometers have 
been devised ; and some of them no doubt answer 
fairly well ; but theoretical objections may be raised to 
all. Those that, whilst giving effective shelter from the 
sun, are more or less freely open, are thought to per- 
mit radiation to or from distant bodies — houses, walls, 
or even the sky. Those that are closed from this 

Air Tcuiperatiire : its Distribiition & Range. 6i 

source of disturbance are, on the other hand, thought 
to be too confined, and not to allow free access of air. 

At the Royal Observatory at Greenwich the stand 
which is in use is a modification of what is known as 
the Glaisher : it may be described as simply a pent- 
house of wood, fixed on a vertical post, round which it 
may be turned, so as always to face away from the sun. 
The double-boarded roof, as well as a vertical partition 
descending from the ridge, certainly screens the thermo- 
meter from the sun's rays, and to some extent from the 
sky ; but this last shelter is apparently imperfect : it 
looks as if rain might occasionally strike inside ; and 
radiation to the surrounding objects is unchecked. 
Still these disturbances seem to be slight ; and the 
Glaisher, or some similar stand, has a wide circle of 

I think, however, that I am right in saying that the 
general feeling of both English and Scotch meteorolo- 
gists is, that open stands are not the best ; that, even 
with their admitted imperfections, closed stands with 
louvre-boarded sides are preferable. The stand now 
adopted at all the observing stations of our Society, as 
well as at those of the Scottish Meteorological Society, is 
that known as the Stevenson, a box with double sides, 
something like a small meat-safe. The real objection 
to the Stevenson stand is that it is too small. I believe 
that if it was twice as big, in every way, it would be a 
very great deal better. But as it is, it is now the one 
in most general use in this country, and has the great 
advantage of rendering the observations strictly com- 

62 Meteorological Lechircs. 

parable with each other ; it may perhaps not be the 
best stand that could be devised, but better even 
than Utopian excellence is absolute uniformity of 

A curious and interesting way of getting over the 
difficulty which we all recognise as involved in the 
question of thermometer stands, has been repeatedly 
tried, with results which tend to give confidence in its 
correctness. A thermometer is tied to the end of 
a string some 2 or 3 feet long, and swung freely 
round and round. This is what has been called by the 
French, from whom we derive the idea, the theniiomctre 
fronde, the " sling thermometer." At first sight, it is 
perhaps difficult to believe that the true temperature of 
the air is to be obtained in this way; but in point of 
fact, except in the full glare of the sun — and it is even 
doubtful whether such an exception is needed — a 
thermometer so slung is found to read within 0'5° of 
one sheltered in a Stevenson stand ; for occasional 
purposes it may be fairly "^ trusted, and will certainl}- 
give travellers a better idea of air temperature than 
such impromptu observations as they are sometimes in 
the habit of recording. 

A point of importance almost equal to that of position 
or shelter, is the time at which the thermometer should 
be observed. The readings of most interest are the highest 
and lowest in the twenty-four hours; but special thermo- 
meters are made to record these automatically. I will 
not attempt to describe the several ways in which this 
record is made. The one now most favoured by English 

Air Temperature : its DistribiUioii & Range. 6 t^ 

observers for marking the maximum or highest reading 
is, I think, that which was invented nearly fifty years 
ago by the late Professor Phillips : about an inch of the 
upper part of the mercurial column is separated from 
the main body by a small bubble of air; this, as the 
temperature rises, is pushed up ; when it falls, is left 
behind ; stranded, as it were, at high-water mark. 
To mark the minimum has been found more difficult; 
and though many ingenious methods have been pro- 
posed, I do not know that any can be considered 
quite satisfactory. The one to which there are fewest 
objections is perhaps that known as Rutherford's mini- 
mum thermometer, in which the temperature is shown 
by a column, not of mercury, but of spirit ; this, on con- 
tracting, drags with it a small light index, which it flows 
past on expanding again. Another interesting form of 
thermometer, now nearly a hundred years old, and known, 
after its inventor, as Six's, records both the maximum and 
minimum. The cost and complex arrangement of this 
thermometer has prevented it from being generally used 
for observations of air temperatures ; but it has rendered 
valuable service in the deep sea ; and since the improve- 
ments suggested about ten years ago by Dr. Miller, and 
carried out under his directions by Mr. Casella, it has 
become recognised as the only instrument to be 
depended on when subjected to great pressure. This 
thermometer known commonly as the Miller-Casella, 
was used on board the "Challenger." 

But more recently still, Messrs. Negretti and 
Zambra have invented a thermometer for taking deep 

64 Meteorological Lectures. 

sea temperatures, which, if it does not supersede the 
Miller-Casella, will at least probably be found a useful 
auxiliary to it; for whilst the Miller-Casella registers only 
the lowest temperature met with, at whatever depth, 
this of Messrs. Negretti and Zambra registers the 
temperature at the bottom. The instrument is so in- 
genious, so new, and as yet so little known, that I 
think you will readily pardon me if I dwell for a minute 
or two on its construction. 

The thermometer itself, like the well-known maxi- 
mum thermometer invented by the same makers, has a 
small obstruction in the throat of the tube, near the 
bulb ; this answers as a valve, past which the mercury 
readily flows as it expands ; but past which, when the 
tube is horizontal, it cannot return. But differing from 
this, the deep-sea thermometer has a siphon-shaped 
tube, and is fixed in a case, so that whilst it is being 
lowered through the water the instrument remains ver- 
tical ; but as soon as it begins to ascend, the upward 
motion brings the pressure of the water on the upper 
surface of a broad screw, which is thus made to revolve 
in the opposite direction, and by means of a small cog- 
wheel, to turn the thermometer completely round, thus 
pouring all the mercury above the stop into the other 
leg of the siphon-shaped tube, where it remains till it 
is read off. The instrument has not yet, I believe, been 
tried — or at least fully tried — at any considerable 
depth, so that it is impossible to say that it will cer- 
tainly answer when under great pressure ; but it seems 
probable that it will, and be a valuable auxiliary to, and 

Air Temperature : its DistidbiUion & Range. 65 

check on, the older instrument, which, with all its 
merits, has some serious faults, and requires always very 
great care. 

As an instrument for correctly observing air tem- 
peratures, this thermometer promises to be even more 
useful : it can be attached to some very rough clock- 
work, which will turn it over at any set time, just as an 
alarum will go off ; and in this way a row of them may 
be turned over, one every hour, or one every two hours, 
and the temperature recorded twenty-four or twelve 
times a day, without further trouble to the observer 
than reading them off, all at the same time, resetting 
them, and winding up the clocks. 

For, apart from the maxima and minima, we want 
to know also the mean temperature ; and for this, with 
ordinary thermometers, we must determine when they 
should be observed, in order from a few readings to 
calculate a true mean ; or, in every-day words, to strike 
a fair average. On this point there has been a very 
great difference of opinion. If the thermometer could 
be observed every hour, or every two hours, the sum of 
the 24 or 12 readings, divided by 24 or 12, would be 
accepted as a mean without dispute. But only in the 
largest observatories, with a regularly organised staff of 
observers, has this been possible. We are, for the most 
part, obliged to rest content with two or perhaps three 
observations. This being the case, it is a very import- 
ant question when these two or three observations 
should be made. The convenience of the observer — 
generally a man with some business to attend to — must 

66 Meteorological Lechircs. 

necessarily have great weight in the decision ; and 
taking this into consideration, our Society, whilst insist- 
ing on uniformity for the sake of comparison, has 
resolved that at all its stations the observations are to 
be made at 9 A.M. and 9 P.M. These are not only the 
most convenient hours for the greater number of amateur 
observers, but they are the best of any two for giving a 
mean temperature. Different methods of obtaining a 
mean from them have been proposed. Thirty years 
ago Mr. Glaisher published a table of corrections, by 
which the mean observations at any hour might be 
turned into the mean for the day ; and other similar 
corrections have since been proposed by the Smith- 
sonian Institution. It is, however, more than doubtful 
whether any one set of corrections is applicable to obser- 
vations at different stations, or even at the same station 
in different months ; and the Society, recognising that 
half the sum of the mean readings at 9 A.M. and 9 P.M. 
is rather below the mean temperature, and half the sum 
of the mean maxima and minima is rather above it, 
now publishes these four readings for each day, and 
suggests that their sum, divided by four, will not differ 
more than o°"5 from the true mean, and may — should 
it at any future time prove desirable — be corrected 
according to any method then established.^ 

^ The general opinion of the Society may be gathered from a paper 
laid before it in March 1877 by Mr. Marriott, and from the discussion 
which followed {Quarterly Joiirtial of the Meteorological Society, new series, 
vol. iii. p. 399 et scq.) ; but more certainly from the action of the Society 
in regard to its observing stations, as shown in the report on them in 
No. 27 of the your rial. 

Air Temperature : its DistribiUiofi & Range. 67 

Undoubtedly the best and truest means are to be 
got from the continuous record made by photographing 
the registering point of the mercurial column of the 
thermometer. This is either the top of the column, as 
at Greenwich, or a small air bubble interposed in a 
longer column, as at Kew and the other principal 
stations of the Meteorological Office ; but in either case 
the mark of it is thrown, by a carefully-adjusted lamp, 
on a sensitive paper, wound round a cylinder or drum, 
which revolves by clock-work once in the twenty-four 
hours. To such a trace a scale is easily applied, which 
translates it into degrees at any wished-for hour ; but 
its great advantage is, that by measuring the area cut 
off, the mean height of the trace, that is, the mean tem- 
perature, may be calculated without much difficulty, and 
with the greatest possible exactness. 

Before leaving this subject I should like to bring to 
your notice one more instrument, which must as yet, 
perhaps, be considered as experimental, but which is 
one of the most ingenious, and may possibly prove one 
of the most useful of all registering thermometers. Its 
inventor, Mr. Stanley, has called it a chronothermo- 
meter, or thermometrical clock ; it is, in fact, a clock, 
registering on its dial the beats of its pendulum pretty 
much as other clocks do ; but its peculiarity is this, 
that the pendulum is a species of air thermometer, so 
fitted that the expansion or contraction of the air forces 
mercury out of a lower cistern into a higher, or allows 
the mercury to run back from the higher into the 
lower. The centre of oscillation is thus subject to a 

68 Meteorological Lectures. 

continual change.^ Any one who knows how to regu- 
late an ordinary kitchen clock will at once see how the 
chronothermometer will go faster for an increase of 
temperature and slower for a decrease. The difficulty, 
of course, is in the adjustment. Mr. Stanley considers 
that he has overcome this ; that the pendulum will beat 
faster or slower at a true rate, now corresponding to 50 
beats a day for each degree of temperature, and that 
this may be advantageously made to correspond to 200. 
The instrument will thus record the mean temperature 
for any reasonable length of time — a day, a week, 
a month, or a year — with perfect accuracy, and without 
any calculation. If, in addition to this, it can be made, 
as I think it may be, by a continuous succession of 
electric contacts, to record each beat, and thus register 
not only the mean temperatures, but the temperature at 
every second of time, the scientific value of the instru- 
ment will be far beyond that of any ever yet made. 

And now I must stop ; not that I have exhausted the 
subject, but that I have already taxed your patience 
too long. I can scarcely doubt but that much of what 
I have said has sounded to many of you as a twice-told 
tale, though some indeed may have thrown the know- 
ledge of it on one side and forgotten it. To such I 
may express a hope that the recalling of old memories 
has been not without pleasure. But to others, to whom 
what I have said may have come with the force of 

^ A detailed account of this instrument, and its fellow, the chrono- 
barometer, will be found in the Society's y^wrwrt/ (new series), vol. iii. pp. 

Air Temperature: its Distributio7i & Range. 69 

novelty, to those who have hitherto paid but little 
attention to this branch of science, whether it be called 
Geography or Meteorology, if I have been fortunate 
enough to awaken your interest, to have induced you to 
turn towards it for the future, I am so far your bene- 
factor, that I have found for you another charm in life, 
that I have enlisted you as students in the service — I 
will not say of science, but of nature ; that goddess ever 
fair, ever free ; whose beauty age cannot wither, whose 
infinite variety custom cannot stale. 



In the first Lecture of this course Dr. Mann explained 
the Torricellian experiment, which was the origin of the 
barometer, so that it is not necessary to do so again. 
This experiment was invented by Torricelli in 1643. 
It was one of many experiments made by him with 
the object of investigating the cause of the rise of fluids 
into vacuous tubes, and this one in particular led to the 
discovery of the pressure of the atmosphere, due to the 
weight and elasticity of the air and vapours of which 
it is composed, and, moreover, gave an exact means 
of measuring that pressure. So productive of conse- 
quential results to science, so many highways and bye- 
ways of knowledge has it pioneered, that on this single 
experiment the imperishable fame of Torricelli reposes. 
He died at an early age ; and though he achieved 
other successes in science, he and they would have 
been long since lost in oblivion but for this capital ex- 
periment. He even used a tube turned up at the open 
end, thus forming the first siphon barometer, with 
which instrument he detected variations in the atmo- 
spheric pressure. In endeavouring to show how the 
barometer has gradually been perfected into an instru- 
ment of precision, we start from this experiment as the 

The Barometer and its Uses. 7 1 

initial instrument. Torricelli gave it no specific name ; 
apparently he did not regard it as an instrument, but 
merely as a philosophical experiment, and for a long 
time it was known by no other name than Torricelli's 
experiment, or the experiment of the vacuum. Such, 
however, was the origin of the barometer, an instru- 
ment of the first importance in meteorology, which has 
led the way to the invention of the air-pump, the fire- 
engine, the hydraulic ram, which act by the elasticity 
and pressure of air, and of the steam-engine, which, as 
first constructed, was dependent on the pressure of the 
atmosphere for its efficiency. The barometer has also 
enabled scientific men to define the laws of fluid pressure, 
and the laws of relation between pressure, temperature, 
and volume of gases and vapours, so that in physics 
and chemistry it has been of essential service. It con- 
tinues to be indispensable in the practice of these 
sciences, and in the working of the steam-engine. But 
with these matters we are not now concerned ; our 
attention is entirely directed to the barometer as a 
meteorological instrument. 

Disputations on the validity of Torricelli's discovery 
of the pressure of the atmosphere were happily con- 
fined to a short period, for they were at once and for 
ever cut short by Pascal, whose celebrity as much de- 
pends upon his crucial experiment with the barometer 
as Torricelli's on its invention. Pascal repeated the 
various experiments made by Torricelli, and satisfied 
himself of the pressure of the air, and the consequent 
rise of fluids into vacuous tubes. It then occurred to 

72 Aldeoi'ological Lectures. 

him that the TorricelHan cokimii must be affected by 
the quantity of air vertically above, and not at all by 
that below, its level ; and, therefore, that its length 
must be proportionally diminished in elevated places. 
Accordingly, in 1647, he requested Mons. Perrier, his 
brother-in-law, to perform the Toricellian experiment on 
the summit of the Puy de Dome, a mountain near his 
native town, Clermont. It was not until 19th Septem- 
ber 164S that Perrier could obtain sufficient leisure and 
a favourable opportunity to carry out the project. Early 
on that day, a memorable one in the history of meteor- 
ology, he assembled a distinguished party of ecclesias- 
tics and seculars in Clermont, where, and in their pre- 
sence, he several times performed the Torricellian 
experiment. The party then proceeded to the summit 
of the mountain, about 8 miles distant, where he 
also several times made the experiment, with this result, 
the column was 3"33 inches shorter than in the town. 
On the way down, at Font de I'Arbre, they found the 
column had an intermediate height. Thus he clearly 
proved that the air below the instrument had no effect 
upon it. Time would fail us to enter into particulars of 
this memorable expedition, or to describe the scrupu- 
lous care with which the experiments were carried out, 
and repeated again and again, so as to eliminate all 
sources of doubt. Suffice it to say, that if to-day we 
calculate from Perrier's data the heights of the stations 
Avhere he observed, the results are surprisingly in accord- 
ance with the most recent measurements. Thus his 
observations give 3458 feet for the height of the Puy de 

The Barometer and its Uses. J-^ 

Dome above Clermont, and the actual height is now 
stated to be 35 1 1 feet. 

After giving brilliant proofs of scientific abilities of 
the first order, Pascal devoted himself entirely to a reli- 
gious life, and died at the early age of thirty-eight. 
After his death his treatises on the " Equilibrium of 
Fluids," and on the " Weight of Air," were published by 
Perrier, in 1663. These contain the recital of the Puy de 
Dome experiments, and show how the Torricellian 
column may be used to judge of the state of the weather. 
Pascal found that it has a range of v6 inch in France ; 
that it is generally higher in winter than in summer. 
Readings of the Torricellian column were taken daily by 
Pascal at Paris, by Perrier at Clermont, by Chanut and 
Descartes at Stockholm, during the years 1649-50, at 
the same time, " in order to see if anything could be dis- 
covered by confronting them with one another." Pascal 
was thus the pioneer of the synchronous observations 
upon which modern storm-warnings depend. 

Boyle, in 1665, observed the Torricellian column in 
relation to the weather, and gave it a scale and lettering. 
Hooke observed its ascent from the effect of augmented 
pressure at the bottom of coal-pits, and invented the 
wheel barometer, or weather-glass, which has been ever 
since a common household instrument Professor G. 
Sinclair, of Glasgow, in 1668 and 1670 measured the 
height of some hills in Scotland. To the instrument, 
fitted up in a frame, he gave the name baroscope, or indi- 
cator of weight. The termination scope was afterwards 
changed to the more definite one meter, and the name 

74 Meteorological Lectures. 

barometer, now for the first time applied to Torricelli's 
invention, is intended to signify a measurer of the weight 
of the atmosphere. However, it must be acknowledged 
that its etymology has hardly this definiteness of meaning. 
We have here specimens of the best modern forms 
of the barometer, Fortin's standard for observatories, 
Gay Lussac's standard for travellers, the Kew marine 
standard. Now, having glanced at these, let us revert 
to the original instrument. Before it could be got into 
these modern patterns, many things had to be found out 
and many improvements made. The original may be 
likened to a child of nature, these modern forms as 
children disciplined by science and adorned by art. 
Without going into details, the improvements which have 
led up to the perfect barometer may be mentioned, i. 
The mercury must be pure. 2. Every trace of air or 
moisture must be driven out of the tube. This is accom- 
plished by the process of heating to a high degree the 
tube while it is being filled, and was first practised by 
Cassini in 1740. 3. The tube ought to be accurately 
vertical. If not, a correction might be calculated and 
used, but in practice there is no difficulty in keeping the 
instrument vertical. 4. The level of the mercury in the 
cup varies with the rise and fall of the column ; and, as the 
column is measured from this level, the relative capacities 
of the tube and cistern must be considered. The capacity 
error may be dealt with in four ways — (i) by a movable 
scale, the zero being always adjusted to the cistern level ; 
(2) a movable base to the cistern — Fortin's invention, 
which allows the cistern level to be raised or lowered to 

The Ba7'ometer and its Uses. 75 

the zero of a fixed scale ; (3) a fixed cistern and a fixed 
scale, a correction being applied to the readings ; (4) a 
fixed cistern, with a fixed scale, but the inches instead of 
being of the true length are contracted so as to read 
corrected for the alteration of level, as in the Kew plan. 
5, Accuracy of measurement being all important in 
science, the scale must not only be accurately divided 
and adjusted, but it must be read off accurately, and to 
aid this a vernier is applied to it. 6. Mercury does not 
wet glass, but is repelled by it, the more so the narrower 
the tubes, hence the necessity for a correction due to 
capillarity. This was early noticed, and experimental 
determinations of its value for different sized tubes were 
made, but it cannot be said to be satisfactorily settled 
yet, as the correction is not a permanent one ; it varies 
with the presence of the slightest trace of moisture, 
oxidation, or impurity in the mercury. 7. Temperature 
affects the length of the column and the scale, so must 
be corrected for. This was only satisfactorily accom- 
plished when physicists had determined the dilatations 
of mercury, glass, metals, and woods. 8. The correction 
for temperature has practically settled the question of 
material suitable for barometer frames in favour of brass. 
Wood, which at first was used generally, is now only used 
for common instruments. 9. The construction of the 
tube has been modified to economise the mercury, and 
to maintain the vacuum. The latter, by the introduction 
of a funnel or pipette, the invention of Gay Lussac, its 
object being to arrest the ascent of air from the cistern. 
It is very useful in portable and marine barometers. 10. 

76 Meteorological Lectiti^es. 

To render the barometer useful on board ship a portion 
of the tube must be contracted to a very fine bore. 1 1. 
When art, working upon science, has done its best, the 
barometer is still imperfect. The residual errors must 
be determined by comparison with a reputed standard, 
such as that at the Kew Observatory, and a certificate 
of corrections obtained. Barometers so verified may 
themselves be considered standard instruments, and it is 
with such instruments that meteorology as a science is 
mainly concerned. In this rapid way only have we time 
to trace the improvements which have made the baro- 
meter an instrument of precision. As regards observa- 
tions from such instruments, we may say with Mr. 
Spottiswoode : — " As soon as a subject becomes a matter 
of strict measurement, or of numerical statement, so soon 
does it enter upon a mathematical phase. This phase 
may, or may not, be a prelude to another in which the 
laws of the subject are expressed in algebraical formulae 
or represented by geometrical figures. ... It is not so 
much elaborate calculations or abstruse processes which 
characterise this phase, as the principle of precision, of 
exactness, and of proportion."^ 

Fortin's barometer is the best standard for stations. 
Its cistern constitutes its peculiar feature. Its base is 
flexible, and its upper portion is a glass cylinder. The 
arrangement enables the observer to adjust the level of 
the mercury in the cistern to zero of the scale at every 
observation, so that the instrument has no capacity error. 
Loss of a little mercury from the cistern by oxidation or 
1 Address to the British Association 1878. 

The B areometer and its Uses. 7 7 

leakage is of no consequence, and no alteration of the 
scale and frame is required for fitting a new tube. 

The siphon barometer forms the best standard for 
travelling purposes. It can be made lighter than any 
other kind of barometer, and spare tubes filled with 
mercury can be carried to replace a breakage, as the tube, 
being read from both limbs, can be inserted in the frame 
v/ithout any definite adjustment to the scale. The 
mercury in the open limb gets oxidised and dirty, and a 
bubble of air is very likely to get into the lower portion 
of the column. It was to prevent the ascent of air into 
the vacuum that Gay Lussac invented the pipette. As 
the air can only find its way between the mercury and 
the glass, it ascends as far as the shoulder of the pipette, 
but can get no farther. The presence of an air bubble 
in the column must, however, cause it to read too high, 
when it occupies a portion of the contracted bore ; care 
ought, therefore, to be taken to see that no air is there. 

The barometer has been used at sea since the begin- 
ning of the eighteenth century ; however, it was not till 
the year 1853 that a satisfactory standard marine baro- 
meter was contrived. This was the work of P. Adie, 
under the supervision of the Kew Observatory Com- 
mittee. Its main features are a suitably contracted tube, 
having a pipette, a brass frame, a closed cistern, and a 
scale of contracted inches. To ensure the fitness of a 
barometer for use at sea as a standard meteorological 
instrument, it must be tested to ascertain, on the one 
hand, that it is not liable to "pumping" from the motion 
of the ship, and, on the other hand, that it is not unduly 

78 Meteorological Lectures. 

sluggish. It must also be compared in an air-tight 
chamber, throughout the range, 31 to 27 inches, with a 
standard barometer to obtain its errors. The corrections 
thus found include errors of graduation, capacity, and 
capillarity, are generally confined to the third decimal 
of an inch, and are frequently nil. Further, to adapt the 
instrument for use in ships of war, the covered up portion 
of the tube is packed with vulcanised indiarubber to 
protect it from vibrations and concussions as much as 
possible. A more perfect marine barometer could hardly 
be desired. Leakage from the cistern, or a new tube, 
vitiates the corrections, which must be re-determined. 
It is the most portable of all barometers. 

The barometer has always been vaunted as a weather 
oracle, but it really has no pretences to such a dignity. 
It simply shows the statical pressure of the atmosphere 
above it. This pressure must change before there can 
be any v^ariation in the barometer, supposing of course 
that it is kept in the same temperature. The air puts 
the mercury in motion, hence inertia and friction must 
cause the column to change after, not with, certainly not 
before, the air pressure varies. If it be admitted that 
every wind has its weather, then to observe the direction 
and the force of the wind is the first step to observe the 
weather. Now the wind is a dynamical condition of the 
air, one which we are accustomed to roughly estimate 
from our sensation, and it is very advantageous to have 
in addition an exact measure of the statical condition of 
the air at the same time, which the barometer gives us. 
We gauge then not only the horizontal movement of 

The Barometer and its Uses. 79 

the air but its vertical mass as well, and with the two 
estimates we are better enabled to judge of proximate 
changes than with either alone. However, the practice 
has been, for the most part, to relate changes of wind 
and weather to the state of the barometer ; and innumer- 
able rules have been propounded to enable every one to 
become weather-wise by the aid of a barometer. Torri- 
celli began them, Pascal and Perrier added to them, 
Halley, Patrick, Saul, and others extended them ; some- 
thing to do in this line was even left to Dalton, Jenyns, 
and Glaisher. I am free to say that I have not found a 
single rule, properly so called, among them. By rule, I 
mean a mode of arriving at certain results from deter- 
minate conditions. They are all mere connotations of 
the weather, with the heights and movements of the 
barometric column. They served a useful purpose so 
long as the barometer was used by every one as if there 
was no other barometer in the world, and will continue 
to do so. When the behaviour of barometers in different 
regions and countries came to be known, these connota- 
tions were thrown into a little confusion. A sort of 
elixir of them had been distilled and bottled up on the 
barometer scale, to satisfy the craving for condensation, 
for knowledge formulated — in short for science, which 
humanity manifests. I refer to the lettering on the 
scale, with which we are all familiar, which, however 
little objectionable in cities like London and Paris, when 
it got abroad among the hills and mountains, in the in- 
terior of continents, and away on the oceans, appeared 
sometimes grotesque, not to say absurd. In the main. 

8o Meteorological LectiLvcs. 

it is progress alvvay, however hampered by mediocrity 
or imperfection of instruments and methods. The latest 
connotators introduced some reasoning, especially I will 
refer to that eminent meteorologist, James Glaisher. 
He says : The height of the barometric mercury is 
almost constantly changing ; the average daily varia- 
tions during the year, at Greenwich, are as follow : — 
On 132 days the change is less than O'l inch. 
123 „ it exceeds 0"i and is less than 0"2. 
61 „ „ -2 „ -3. 

27 » » -3 » •4- 

12 „ „ '4 „ -S- 

6 „ „ -5 „ -6. 

4 >. ,. '6 „ ro. 

and on one day in ten years the variation may amount 
to 1-25 inch. It is the changes which constitute the 
barometer an indicator of approaching weather. What- 
ever may be the height of the mercury, a sudden and 
rapid fall is a sure sign of foul weather, and the quicker 
and more sudden the sooner the change will be over. 
Mr. Glaisher has deduced the following relations between 
the velocity of the wind and the height of the barometer 
at the sea level: — Above 30 inches, 130 miles a day; 
about 30 inches, 160 miles ; 30 to 29'5 inches, 210 miles ; 
29*5 to 29 inches, 260 miles ; below 29 inches, 320 miles. 
These are not to be assumed as the normal relations 
between the varying weight of the atmosphere and the 
rates of horizontal motion of the air, but rather regarded 
as expositions of the fact that as the pressure decreases 
the motion of wind increases. " The barometer," says 

The Barometer and its Uses. 8 1 

Mr. Glaisher, " may be almost neglected by the sailor 
when its readings range above the average, but when 
they descend below the average it is a warning which 
ought never to pass unheeded ; and when the depression 
is sudden it is the sure and certain warning of the ap- 
proach of storms." Hence the use of knowing in a 
general way the average height of the barometer — the 
geographical distribution of barometric pressure. Sir 
John Ross said : " In high southern latitudes, the baro- 
meter at 29 inches we learned to consider to indicate 
fine weather, although in England such a depression 
would be regarded very differently ;" and Captain Maury 
said: "The seaman observes his barometer and finds it at 
29-3 inches ; now if he be in 56° N. he may look out for 
squalls, but if he be in 56° S. it is only the mean height of 
the barometer, or what 299 inches would be in 56° N." 

The connotators were succeeded by the cyclonists, 
Franklin, Capper, Redfield, Reid, Thorn, Piddington. 
These investigators of the laws of storms took baro- 
meters into their confidence, although they were very 
untrustworthy, being badly made, inaccurately measured, 
carelessly observed and reduced. Thus two barometers 
in the same ship read as in margin. Still their confidence 
was not misplaced. They discovered that the distribu- 
tion of atmospheric pressure was symmetrical within the 
storm area ; that while all great storms and tempests 
exhibit a wind blowing around a calm nucleus, this 
nucleus has the lowest barometer, and that the pressure 
increases all around to the very limit of the storm. 
This was a gigantic advance, and these important in- 









82 Meteorological Lectures. 

vestigations assumed the shape of laws of storms, about 
which big treatises were written, which became of in- 
estimable service in the art of navigation. Dove seems 
to have endeavoured to reconcile the connotations with 
the laws of storms in his work on the gyratory theory 
of the winds. He succeeded in bringing a large number 
of connotations under the regime of reason, and to 
marshal them into some sort of order. Admiral Fitz- 
Roy, in the Barometer Maiuial, seems to have attempted 
to put the connotations into order on Dove's ground- 
work. It was intended for fishermen, boatmen, and 
pilots, not the knowing old salts who take leave of the 
land, certainly not. I have often wondered how much 
the poor fishermen must have puzzled over it.. 

In the earliest attempts at measuring heights by the 
barometer, the atmosphere was regarded as possessing 
the same density throughout its whole extent, which 
was found to be quite erroneous when the elevations 
were considerable. The next idea was, that the density 
of the air decreased as the altitude increased, but this 
was found not to suit the circumstances. In 1685 the 
famous Halley proved the theorem on which the calcula- 
tion is now founded, and which establishes that, the 
heights being taken in arithmetical, the corresponding 
densities of the air follow a geometrical progression. 
Uniting practice with theory, Halley, in 1697, observed 
the barometer at the level of the sea and on the summit 
of Snowdon, and found it to stand respectively at 299 
and 26'i inches. From the known height of the moun- 
tain he was enabled to conclude that the air doubles its 

The Barometer and its Uses. 83 

rarity for about three miles and a half of ascent. Much 
remained to be found out regarding the specific gravity 
of air and mercury, the effect of gravity and of tempera- 
ture on both. The problem was improved or modified 
by Deluc, Horsely, Damen, Playfair, Roy, Schuckburg, 
and others ; but its now generally accepted formula is 
due to the celebrated Laplace. Not to pursue this sub- 
ject further, it may be shortly said that the barometer, 
or its substitute the aneroid, is now an indispensable in- 
strument for contouring and levelling, especially where 
methodical surveys cannot be conducted, or where 
rapidity of results is desired. 

As the elevation above the sea, or any other level, 
can be determined by barometrical observations, of 
course the problem may be reversed ; the elevation of 
the barometer being known, its reading may be reduced 
to what it would have been at the sea-level ; and this 
form of the problem is of the utmost importance in 
meteorology. It is impossible to compare the readings 
of barometers at different places until they are reduced 
to the sea-level. The laws of storms having been in- 
vestigated from the data afforded by ships' logs, the 
barometers were all at the sea-level ; when, however, the 
investigation was extended to the land, the barometric ob- 
servations could not be usefully compared until reduced 
to the normal level. Now this important reduction is 
effected by means of Laplace's formula, and the consistent 
results which are every day and everywhere got from it, 
testify to the substantial accuracy of the vast amount of 
science which it encloses, as it were, in a casket. 

84 Meteorological Lect7i7xs. 

The ordinary observations of wind, the rough nota- 
tions of the weather, together with readings from indif- 
ferent barometers, furnished by ships' log-books, sufficed 
for the researches which led to the discoveries of the 
laws of storms. More precise observations, and especially 
careful readings from accurate barometers, conducted 
to the grand generalisation that the so-called laws of 
storms are the laws of the winds everyv/here and always. 
Thus scientific men have learned that no accurate and 
abiding progress can be expected from meteorological 
research, unless accurate instruments, precision in obser- 
vation, and systematic methods are employed. Upon 
such a basis, Admiral FitzRoy, in i860, was enabled, 
aided by the electric telegraph, to inaugurate a system 
of storm-warnings and weather-casts. Leverrier, indeed, 
had advocated the storm-warnings previously. FitzRoy 
was deeply imbued with the views of the cyclonists, and 
especially with the theory of Dove, which favoured the 
assumption that all winds were cyclonic, and in acting 
upon them practically he was perfectly right, but failing 
to make his viev.'s intelligible they were universally 
mistrusted by scientific men. In 1863 Galton came to 
his assistance, though he does not appear to have recog- 
nised it, for in liletcorographica the law of wind in rela- 
tion to the distribution of atmospheric pressure is clearly 
expounded. The charts in this work, though they repel 
examination from the appearance they have to speci- 
mens of the Pekin Gazette, or to a Chinese spelling-book, 
are nevertheless clad in bright auroral colours in the 
memory of all who know them^. They will become in 

The Barometer and its Uses. 85 

time of fabulous value, for they were the earliest of 
Aveather maps ; and it is somewhat significant that we 
are indebted to the same author for the main features 
of our daily weather charts, lithographed as we get them 
by post, or stereotyped as in the newspapers. The 
text to MeteorograpJiica appeals to these charts of 
Western Europe as showing that the areas of barometric 
elevation and depression are enormous, and in their 
main features very regular, but ever changing their con- 
tours and their sections, whilst they also vary in the 
speed and direction of their motion of translation ; that 
the areas of calms are invariably the centres of whirls 
of wind, or are situated between conflicting currents, 
and that there is one marked condition of temperature 
and cloud in connection with the wind, which is per- 
sistent, beautifully marked, and full of interest, namely, 
that a westerly wind is accompanied by an overcast sky 
and a warm temperature, while with an easterly wind 
the sky is pure, and the cold intense. Further, they 
testify to the existence, not only of cyclones, but of what 
the author terms anticyclones. To quote verbatim, " one 
universal fact is, that on a line being drawn from the 
locus of highest to the locus of lowest barometer, it will 
invariably be cut more or less at right angles by the 
wind, and especially that the wind will be found to strike 
the left side of the line, as drawn from the locus of 
highest barometer. In short, as by the ordinary well- 
known theory, the wind (in our hemisphere), when in- 
draughted to an area of light ascending currents, whirls 
round in a contrary direction to the movements of the 

86 Meteorological Lectures. 

hand of a watch, so, conversely, when the wind dis- 
perses itself from a central area of dense, descending 
currents, or of heaped-up atmosphere, it whirls round in 
the same direction as the hand of a watch." Professor 
Ballot, of Utrecht, claims to have enunciated this general 
law of the winds before Galton, but he certainly proved 
it only for the small area of Holland. Subsequent re- 
search has now enabled meteorologists to define the 
general law of the winds all the world over, in this con- 
cise form : — The wind blows along the isobars or lines 
of equal barometric pressure, with a less pressure on 
the left of its course than on the right, in the northern 
hemisphere, and the converse in the southern. 

So long as barometric observations were made at 
independent stations, and were not confronted with each 
other in respect to the same instant of time, all that 
could be deduced from them were hourly, daily, monthly, 
and annual averages. The majority of observers could 
only record observations once or twice daily with regu- 
larity, and these yield averages for the particular hours. 
It was soon discovered that the barometer had a diurnal 
variation, and an annual variation, so that, in order to 
discover the laws of these periodicities, a barometer 
constantly registering its height was required. Hence 
the invention of self- registering barometers, or baro- 
meters in mechanical connection with clockwork, of 
which there are several kinds, the best being the so- 
called barograph, perfected at the Kew Observatory, 
and used at the British Meteorological Observatories. 
It may be shortly described as a standard barometer. 

The Barometer ajtd lis Uses. Zj 

which is caused to photograph its fluctuations during 
day and night, clockwork carrying the sensitised paper 
round in front of the barometer. The daily barograms 
become records from which the values may be measured 
off for any required instants. The curve, reduced, may 
be published entire as in the Quarterly Weather Reports ; 
which reduction itself is effected by a marvellous com- 
bination of scientific apparatus and skill. Means de- 
duced for each hour of the day enable us to detect the 
diurnal range ; the means of daily values for the months 
give the monthly values, which show the annual range ; 
finally, the monthly values yield an annual mean. 

As regards diurnal range, it exhibits generally two 
maxima and two minima, is greatest in amplitude and 
most regular in tropical countries, is lessened by increase 
of latitude and by elevation above the sea. Its epochs 
vary with localities and seasons. In Polar regions it 
almost vanishes. In tropical and temperate regions the 
times of maxima and minima are, roughly speaking, 
9 A.M. and P.M., and 3 A.M. and P.M. In the tropics the 
phenomena of the barometric range are so constant that 
Humboldt remarked that the time of day might be in- 
ferred from them within seventeen minutes. If we 
remember that this is the amount of the equation of time 
in some months, their period becomes identical with the 
solar day, or the cause of the diurnal range of atmospheric 
pressure is to be sought for in the sun's action. Now 
solar heat raises and lowers every day the centre of 
gravity of the air over any given meridian ; but this is 
a simple not a double period. The action of the sun, 

88 Meteorological Lectures. 

therefore, must be indirect, taking effect through an 
intermediate agent. That agent is probably the vapour 
of water always present in the air, ever varying, now 
invisible gas, again visible vapour, then gone as water. 
Aqueous vapour, visible or invisible, has a greater absorp- 
tive power for luminous heat than dry air. As the heat 
of day increases the vapour rises faster. The more it is 
diffused, the more of the solar rays it arrests, so that its 
tension goes on increasing till the hottest part of the day ; 
after this it declines : it has, in fact, a maximum and a 
minimum, corresponding very closely with the diurnal 
curv^e of temperature. The atmosphere of dry air, on the 
contrary, has a minimum pressure about midday, when it 
is most expanded, and a maximum about midnight, when 
it is most contracted. The two periods of vapour 
tension and dry air acting together give the double period 
to the barometric column. This theory was broached by 
Dove, and supported by Sabine. It has been said that 
no scientific theory can be considered complete until it 
is so clear that it can be explained to the first man you 
meet in the street. Well, this theory certainly admits of 
sufficiently simple explanation, and any one might 
explain it to any man in the street to their mutual satis- 
faction. See here, for Toronto, the curve of vapour tension 
is very similar to a curve of diurnal temperature. It has 
a maximum about the hottest part of the day and a 
minimum about the coldest ; the curve of the diurnal 
pressure of dry air is similar but reversed, the minimum 
occurring at the hottest part of the day, the maximum at 
the coldest. Combining the ordinates of the two curves. 

The Barometer and its Uses. 89 

the result is the barometric curve, which exhibits a 
double period, two maxima and two minima, at about 
10 A.M. and P.M., and 4 A.M. and P.M., respectively. But 
let us go to Ascension, and the case is altered. We still 
have a double period for the diurnal range of the baro- 
meter, but the vapour tension and the dry air pressure 
of which it is composed both exhibit a double period 
also. Such cases completely demolish the theory. The 
diurnal range of vapour tension does not always and 
everywhere conform to the simple oscillation. The 
capricious behaviour of vapour is, on consideration, quite 
inconsistent with such a theory ; every cloud in the sky 
is a visible protest against it. A hypothesis then re- 
mains yet to be framed which shall account for the 
diurnal range of the barometer in all seasons and places. 
In the suspended diagrams the meteorological 
curves for diurnal range are exhibited for Toronto and 
for the Island of Ascension, and the subjoined table 
contains the data from which they have been drawn. 
The curves of temperature are not shown ; however, it 
will be readily understood that at Toronto not only does 
the curve of diurnal range of vapour tension follow the 
march of diurnal temperature, but that of the wind's 
direction does the same, and it would seem that the curve 
of wind force is of the same character, namely, attaining 
a maximum about the hottest part of the day and de- 
clining to a minimum about the coldest part of the night. 
At Ascension, although the vapour tension is so much 
greater than at Toronto, its variations are less, and its 
diurnal curve has two maxima and two minima. The 


Mdcorolos'ical Lectures. 

abrupt turn of the curve of dry air pressure at 1 1 A.M. 
seems to point to error either in the observations or the 
reductions, as nature never acts in such a way. Then, 
as regards the wind's direction, it is so constant that it 
hardly shows any diurnal range. The force of the wind, 
however, exhibits unmistakably the same features of 
diurnal range as at Toronto. 

Diurnal Range of the Barometer, Vapour Tension, Pressure of 
Dry Air, and of the Resultant of the Wind Observations.' 

I. Toronto, 
II. Ascension, 

1S42, July 1st, to 1848, June 30th, six years. 
1863 to 1865, two years. 






Ten- P 








Va- E 










pour. A 


A M 






Inch. Inc 










0-645 29 


S 52° E 



















































































2 24 






















2 37 





































31 "2 











































































































23 '9 












' The Toronto winds are results of the years 1854-0. 

The Barometer and its Uses. 9 1 

The annual range of the barometer is not so well 
defined as the diurnal, though no doubt it is dependent 
on the agency of aqueous vapour, both air and vapour 
being influenced by the sun's annual course. It is a 
curve of a single period, the maximum occurring in 
winter, the minimum in summer. . The range of the 
barometer was first noticed by Dr. Beale in 1666, and its 
nature and causes have engaged the attention of philo- 
sophers ever since. Early in this century our know- 
ledge of it in different parts of the globe was greatly 
increased by Humboldt, Ramond, Bravais, K^mtz, 
Forbes, Sabine. Several hypotheses have been started 
to account for it. None have stood the test of experi- 
ence ; and the whole subject is still open to investigation. 
Unfortunately the data available in the form in which 
such an investigation requires it are very scanty. As it is 
generally admitted that vapour tension acts an important 
part in the phenomena, especial care ought to be given 
to measure it contemporaneously with the barometer, 
and to deal with it in a correlative manner. This, how- 
ever, is too seldom done ; the best observatories simply 
neglect this important branch of the inquiry. There is 
another circumstance which, during the last fifty years, 
has tended to diminish the ardour of researchers, of re- 
ducers, and of observers, and that is the mathematical 
machinery in which it has been the practice to grind up 
this subject. To such a state of mysticism have these 
long mathematical involutions and evolutions tended, 
that many meteorologists believe that their observations 
are actually improved by passing them through this mill. 

92 Meteorological Lccttires. 

There can be no such virtue in any mathematical for- 
mula ; though such a formula may indeed wrap up, as it 
were in a casket, the soul of the giant, here represented 
by a vast array of figures. I do not say that formulae 
for cyclical phenomena are useless ; but I advise caution 
in their employment. Only those who have worked at 
the mill know the friction, the labour, and the time in- 
volved in the process of passing statistical values into 
formulae, and the reverse ; while the preparation of the 
statistics is so much more needed for solving the problem : 
— What causes the periodic range of the barometer t 

Let us now pass to the subject of geographical dis- 
tribution of pressure. In the first place it may be re- 
marked that, as regards the land, no progress could be 
made in our knowledge of this subject, until accurate 
barometers got into use, and a correct method of reduc- 
ing their readings to sea-level was devised. These 
conditions being fulfilled, barometer observations made 
at different places may be compared in two ways. First, 
they must all be taken at the same instant of time : this 
is the synchronous method. Second, they may be taken 
regularly at each station at any given hour, and the 
monthly values may be deduced from them by applying 
a correction for diurnal range, if necessary ; which is the 
statistical method. The synchronous method is followed 
in the preparation of daily weather reports now published 
bymost governments. Our own official weather reports are 
from observations made at about forty stations on the 
coasts of the British Isles and adjacentseas, at 8 A.M. Green- 
wich time. The barometer observations having been re- 

The Baromda' a7id its Uses. 93 

duced to 32° and the sea-level, isobars are drawn from 
them. An isobar is a line passing through places which 
had at a definite epoch equal readings of the barometer.^ 
Thus, we see that the wind blows nearly along the 
isobars, with the atmospheric pressure always less on the 
left side of its course than on its right ; and that the 
force of the wind is greater the nearer the isobars are 
together. If along a line at right-angles to an isobar 
a distance of 60 nautical miles be measured, and the 
difference of the barometer readings at the extremities 
of this line be taken, this is called a gradient. Hence, 
the greater the gradient the greater the force of the wind. 
Upon these official weather reports forecasts of impend- 
ing weather were made in the first instance by Admiral 
FitzRoy. They were discontinued for some years, and 
have only recently been resumed in a more modest 
fashion. Let us try and understand how the barometer 
helps us to these forecasts. I don't for a moment wish 
to be understood to say that atmospheric pressure, as 
shown by the barometer, causes wind ; I would decidedly 
put the case the other way. However, the indications of 
the barometer are much more accurate than mere esti- 
mates of the direction and force of wind, consequently 
the isobars become exponents of the wind. Given the 
isobars you can infer the winds, and vice versa. Now, 
to fix our attention on something definite, if we could be 
sure that the isobars shown any morning would be the 
same the next morning, we would have at once a fore- 

1 A chart of a cyclone, and a chart of an anticyclone were exhibited, 
with other diagrams and instruments lent by the Meteorological Office. , 


Meteo7^olozical Lecttircs. 

cast of the weather for twenty-four hours at least ; and 
if we even knew how they would appear to-morrow 
morning, we should know how the wind must change in 
the interval, and thus have a forecast. This, you will 
perceive, can only be done by relying on the rate of 
change which is going on in the various barometers. 
Now I find that the mean duration of the rises and of 
the falls of the barometer in our latitudes is 2 days ; 
about 75 per cent of them take longer than twenty-four 
hours ; in exceptional long spells of similar winds and 
weather, they may take from 6 to 1 1 da)'s. Hence, if 
you assume that the movement of the barometer will 
last for 1 1 days, you may make a forecast for that period, 
but the chances of being borne out by the actual weather 
will be very small. In short the chances for a tolerably 
accurate forecast for one day are not more than 75 in 
100. At Greenwich, for the year 1876, the non-periodic 
fluctuations of the barometer were as follows : — 







to Max. 


to Min. 

1 Min. 

to Max. 


to Min. 









Januaiy . 








Februaiy . 















































August . 














October . 


























! 7 




The Barometer and its Uses. 95 

In 1859 Maury wrote that one of the great practical 
questions of the age was a daily system of weather 
reports between Europe and America. We have not 
accomplished this yet. Recently, however, the New 
York Herald has been kindly sending us warnings of 
storms which are on their passage over the Atlantic. 
It is not yet satisfactorily shown that storms ever do 
actually traverse the Atlantic, from America to Europe. 
Nevertheless, it is worth while inquiring how our 
American friends manage this business. They are not 
very willing to show their hands, as the sa\'ing is. How- 
ever, we may surmise how it is done. They have active 
agents who make extracts of the logs of all the steamers 
directly they arrive in New York, and by means of these 
extracts they can follow up all the storms which occur 
in our parallels. Thus it may often happen that infor- 
mation of storms is obtained by the Herald before they 
have had time to reach Western Europe. The Herald 
at once flashes the news by telegraph. We get the 
telegram surely and speedily, and the storm, if it does 
not vanish in due time, shortly afterward. 

]\Ionthly averages of atmospheric pressure have been 
calculated wherever barometrical observations have been 
made ; but so long as they remain secluded in schedules 
in their own observatories, or in reports, their value is 
not known to its full extent. Buchan has undertaken 
the formidable task of bringing them together from 
every know-n source. Thus about four hundred places 
have yielded data, from which he has constructed 
monthly isobaric charts of the world, also a chart of 


Meteo7'oloo;ical Lectures. 

their annual values. Like Atlas, he has taken the world 
in his arms, and girdled it with his isobaric lines. Only 
the general results of this stupendous work can here be 
mentioned. During December, January, and February, 
the atmospheric pressure is greater in the northern than 
in the southern hemisphere, and the converse during 
June, Jul}-, and August. Throughout the year it is 
lowest over the Antarctic Ocean, about 29 inches. In 
the hemisphere where winter reigns, the greatest pres- 
sure lies over the land ; the larger the continent, the 
greater the pressure. In the hemisphere where summer 
reigns the low pressures are over the land, the high over 
the oceans. Some of the most remarkable areas of high 
and low pressures are the following : — 






Iceland . , . 


Dec, Jan., Feb. 


50' X. 170° W. 


50' N. 100^ E. 


0° to 40'' S. 


June, July, Aug. 



40° X. 90' E. . 
30^ X. 40^ W. 


During March, April, and May the distribution is 
more equable, with a tendency to decrease over India 
and Tropical Africa, and to increase over the southern 
hemisphere, especially over the land. During Septem- 

The Ba7'-oi7iete7' and its Uses. 9 7 

ber, October, and November the process of equalisation 
goes on in a contrary direction to that just described. 

It had long been well known that in sailing from 
high latitudes towards the equator, the atmospheric 
pressure increases towards the tropics, and decreases 
thence to the equator. Buchan's investigation enables 
us to take a general view of the subject, and to inquire 
how the distribution of pressure is related to the systems 
of the trades, the monsoons, and the variable winds. 
To be brief, the isobars are related to the prevalent 
winds in accordance to the general law. 

Consequent upon the development of the law of 
wind in relation to the distribution of atmospheric pres- 
sure, there have not been wanting attempts to express 
it in a general mathematical formula. The ablest 
mathematician who has dealt with the subject hitherto 
is Ferrel, in America. Everett in Ireland, Hann in 
Austria, Mohn in Norway, have followed in the footsteps 
of Ferrel, and Laughton, also, has written on the subject. 
They may be called expounders of the centrifugal 
theory of atmospheric circulation and distribution. They 
evidently believe with Newton that "The whole diffi- 
culty of philosophy seems to me to lie in investigating 
the forces of nature from the phenomena of motion, and 
in demonstrating that from these forces other phenomena 
will ensue ... I would that all other natural pheno- 
mena might similarly be deduced from mechanical 
principles." The simplest form to which I can reduce 
Ferrel's final formula is this : 

98 Meteorological Ledtires 


/•524 sin 1 + - cos l\v P 

281 cos 1 



G =r gradient in 60 geographical miles ; 1 = latitude ; 
v = velocity of wind in miles per hour ; 
r = radius of curv^ature of the isobars ; 
P, P , = atmospheric pressure at the place of observation, 
and at the sea-level, respectively. When the place is at 
or near the sea-level P = P , and this factor disappears. 
The barometric gradient thus becomes a function, not 
only of the wind's velocity, but also of the inclination of 
the wind's direction to the isobars, the radius of curva- 
ture of the isobars, and of the latitude. The unfortunate 
feature of the whole matter is, that the theoretical values 
of G, furnished by the formula, are greatly in excess of 
the actual values. We have therefore yet to get a satis- 
factory formula. Meanwhile, without any refinement, 
it may be useful to have a very simple mode of inter- 
•preting gradients into wind force, as estimated by Beau- 
fort's scale, or the converse, for the British Isles, which 
will be correct enough for all practical purposes of judg- 
ing wind and weather at distant places, and proximate 
coming changes. Every hundredth of an inch of the 
barometric gradient in 60 miles may be assumed 
equivalent to a grade of Beaufort's scale of wind force ; 
so that for 'Oi the force is i ; •o'j, 7 ; TO, 10 ; and so on. 
I am of opinion that no satisfactory expression for 
the barometric gradient will be obtained until meteoro- 
logists correct barometric observations for gravity. The 

The Barometer" and its Uses. 99 

mercurial barometer gives, indeed, the weight of the air 
as a scale balance anywhere, but it does not show the 
absolute statical pressure as a spring would do, as the 
aneroid would do if it were an instrument of precision. 
This is owing to gravity, which is greater at the poles 
than at the equator, greater at the sea-level than above 
it. For latitude and the vertical we might easily correct, 
but it seems to me that gravity cannot be the same over 
deep oceans, on shallow waters, on the coasts, and 
among islands even in the same latitude, while on a 
mountain, and in a balloon, it must be different at the 
same elevation, latitude being the same. Until we 
know something definite about this matter, we had 
perhaps better let the correction of the barometer for 
gravity alone entirely. 

I said that* the barometer was not a weather oracle, 
per se, and I equally affirm that the law of pressure, in 
relation to wind, affords no means of foretelling weather 
by itself Fixing attention on areas of pressure, either 
high or low, merely ; the weather changes which attend 
them are only to be forecast by such data as their ex- 
tent and gradients always, and either (i) rate and direc- 
tion of progress ; (2) rate of veering of the wind ; or (3) 
rate of barometric change. The latter two may be 
either for one place or for several distant places. The 
problem has thus a variety of phases, but generally it 
may be stated thus : Given the barometric pressure, wind 
and weather at a place, or region, at a definite instant, 
to estimate the changes during a succeeding interval, as 
a day or two days. Either the translation of the air, 

I oo Meteorological L ectti res. 

the veering of the Avind, or the change of pressure, must 
be assumed as known for the interval, and all the rest 
results as a matter of course. We cannot here go into 
details. To assume translation, veering, and range, or 
even any two of them, is to assume too much ; they 
involve each other. Care must also be exercised not to 
assume too great a rate ; as, for instance, 135° for veer- 
ing is an excessive amount, which leaves no room for 
failure in estimating successes at any one place, by such 
a criterion, though if pushed to its legitimate limit, it 
would accommodate a chaos of cyclones within a few 
degrees of latitude and longitude. As atmospheric pres- 
sure admits of being the most accurately measured of 
these data, rates of change are perhaps best reckoned 
upon its units. 

As regards annual values of barometrical observa- 
tions, no periodicity has yet been traced for them. They 
appear to me to afford the most precise data for investi- 
gating the sun-spot cycle as connected with weather. 
There are no a priori reasons known to me for support- 
ing that theory, and I consider the great amount of 
labour expended in bolstering it up as very much mis- 
applied, and the whole thing as a wild-goose chase, on 
such paths as the rainfall, the black-bulb thermometers, 
and aurorse. In last week's Nature, there is a paper 
on this very subject by Broun, which is well deserving 
of attentive study. Only I would remark that if it 
should be proved that the sun-spot maximum coincides 
with a barometric minimum, and the sun-spot minimum 
with a barometric maximum in India, there must be a 

The Barometer and its Uses. i o i 

region, or regions, where the law is reverse, otherwise we 
should have to account for an abstraction from our 
atmosphere in some years, and an accession to it in 

Had time permitted, but I have too much taxed your 
patience already, I should have liked to have pointed 
oat to you, and to have supported my opinions by those 
of other meteorologists, that statistical results tend to 
show that there is correlation between the meteorological 
elements considered either synoptically or statistically, 
that is to say both in relation to geographical distribu- 
tion as well as in regard to a single station ; and, there- 
fore, it follows that the key to prediction is a foreknow- 
ledge of some one of them. 

In thus tracing the barometer from its invention to 
its perfection, and recounting the information which it 
has afforded us, it seems to me that I have been trying 
to show, however imperfectly and inadequately, how 
knowledge of a certain kind has been accumulated, con- 
densed, combined, and formulated. Now, v/herever I 
find knowledge methodically reduced to order, I call it 
science. If you do the same, then we are agreed that 
we have been engaged with science to-night. And for 
my part T say not an infant science, but a growing science, 
much meriting public appreciation, for the health com- 
fort and prosperity of all of us are more affected by 
it than by any other science, if we would but think 
about it. 

Vu-^ -w^^aT ^-Qyv^u^ ^ ^n ^Jt'TUdtf. 



There is no branch of meteorology in a more unsatis- 
factory condition than that on which I have to address 
you to-night. In the previous Lectures of the present 
course, we were introduced to subjects on which rapid 
progress has been made in the most recent times. In 
their ingenuity of mechanical contrivance, sensitiveness, 
and delicacy of adjustment, meteorological instruments 
are fast rising towards perfection ; and although there 
is, and will be, wide room for discussion as to the best 
modes of obtaining information from our instruments, 
and still more as to the real meaning of the information 
we obtain, there is every prospect of a tolerably speedy 
consensus on these points. In the Lecture of last 
Thursday you entered on a subject on which progress 
of a still more interesting kind is being made. The 
law of storms is a topic which is stimulating enough, 
indeed, has often proved only too stimulating to the 
faculty of the scientific imagination. We feel that a 
complete theory of the movements of the atmosphere 
is attainable, that the problems which such a theory 
presents are not beyond the reach of human inquiry, 
and that we are actually making brisk, though some- 
what hazardous, strides towards the solution of those 

Clotids and Weather Signs. 103 

problems. I am afraid you will meet with some dis- 
appointment when you proceed, as to-night, from the 
subjects which I have mentioned, to that with which 
wc are now to be engaged, the subject of " Clouds and 
Weather Signs." We find ourselves suddenly intro- 
duced to a topic on which the amount of progress to 
be reported is comparatively slight and unsatisfactory. 
I am almost apprehensive that your reflections, as I 
proceed, will be somewhat similar to those we have ex- 
perienced on the sight of the old-fashioned plough, 
almost as simple and unimproved as it was in the days 
of the Pharaohs, in the midst of the agricultural imple- 
ments at the Paris Exhibition. Quite a rustic and 
antiquated air hangs about the subject of weather 
prognostics (one thinks of the word as spelt with a k) 
about signs derived from cloud-caps, whether day or 
night caps, from rising amijalling mists, from morning 
and evening rainbows, and the resulting sensations of 
the shepherds. We seem going back to the days of 
Aratus and of Virgil ; and, unfortunately, I am bound 
to confess that Aratus or Virgil would find themselves 
almost on a level with some meteorologists of the pre- 
sent day upon the subject of weather signs derived 
from cloud observations. Still I shall hope as we go 
on, not only to show you that the application of scien- 
tific principles throws interesting light on particular 
phenomena embraced in our subject, but also (and this 
will be my special endeavour) to indicate to you what 
appear to me to be the dim outlines of a future science 
of cloud-land. Of that science, I confess at the outset. 


104 Meteorological Lectures. 

I am profoundly ignorant, but, if I can awaken without 
being able to satisfy your curiosity, above all, if I can 
suscitate in others that faith in the ultimate achieve- 
ments of this science which I entertain myself, our 
meeting to-night will not be without useful results. 

It may clear our way if I mention at the outset an 
impediment to our progress in this branch of know- 
ledge, arising from the nature of the subject-matter 
itself. Cloud observation is, in a very large measure, 
an incommunicable art. Keenness of sight, coupled 
with the habit of observing phenomena, are, of course, 
its first requisites. To these must be added a special 
interest in the particular class of objects, and the 
facilities of observation derived from a life spent in the 
open air, and in a favourable situation (I need hardly 
say that the proximity of a London fog is most un- 
favourable). Fishermen, sailors, etc., whose vocation 
keeps them much out of doors, and is also intimately 
connected with the changes of the weather, acquire, as 
individuals, a certain amount of proficiency in the art. 
Much of this is pure training of the eye, and cannot, 
by instruction, be made over to another. My own 
earliest recollections are those of looking at the clouds, 
and forming infantine speculations as to the causes of 
their forms and movements, and of being reprehended 
for exposing myself to all states of weather for this 
purpose. The tendency was inveterate, and to this 
day I have spent nearly a twelfth part of my waking 
existence in that occupation. I can now, when only 
the summit of a cloud, 40 miles away, is visible 

Clouds and Weather Signs. 105 

above the distant horizon, state with unfailing certainty 
whether or not rain is faUing from the under surface of 
that cloud. Similarly, from the long habit of watch- 
ing the motions of cirrus, I can detect at a glance a 
movement of these clouds, which most observers, after ''t,*i^A^^.;^j 
standing motionless to watch them for some minutes, 
fail to discern. And when I look at the moon on a 
cloudless night, I always see its motion through the sky. 
This is mere culture of the eye, similar to that which 
enables the Indian to track the footsteps of a wild beast 
among the fallen leaves, where we fail to see the slight- 
est trace ; or by which the Africander farmer of the 
Orange Free State, though not otherwise especially 
long-sighted, can distinguish a horse from an ox at the 
distance of 5 miles. On the other hand, I have met 
with people unaccustomed to the study of the clouds, 
whom I found to be absolutely devoid of the primary 
notions of perspective in looking at a cloudscape, 
actually regarding a solid cumulus as painted on the 
sky, and imagining a horizontal streak of cloud which 
stretches nearly from the zenith to the horizon as rising 
in an inclined column from the earth. These instances, 
both of precision and its opposite, are so extreme as to 
be almost grotesque. Inaccuracy, however, in cloud 
observation, especially in judging the distance, or in 
estimating the relative height, of clouds, is the rule and 
not the exception. For example, when cirrus or cirro- 
cumulus, at a great altitude, is moving in a rapid upper- 
current, while thin clouds nearer to the earth's surface 
are stationary or nearly so, I have found the greater 

io6 Meteorological Lechires. 

number of people whom I have questioned on the sub- 
ject to say, on looking at the sky, that the first-named 
cloud is the lower of the two strata. We find acute 
observers, like Forster, apparently falling into this mis- 
take. Artists even, whom one would expect to make 
a special study of objects which are some of the grand- 
est and most beautiful in nature, seem addicted, as a 
class (they must forgive me for saying it), to the habit 
of representing the impossible in their cloud portraits. 
I shall have, however, in a few moments again to touch 
upon the subject of painting in connection with this 
branch of meteorology. What I insist upon here is the 
necessity of individual experience in this particular study, 
and the impossibility of imparting the art of cloud 

Now you will naturally say, we are not desirous of 
acquiring the art ; we want the results of the observa- 
tions. It is the business of the specialist not to tell us 
of the difficulties of his work, but to give us some of 
its fruits. A lecturer on mineralogy must not take up 
the time of his audience by descanting on the labour of 
distinguishing between the varieties of minerals, but 
must point out the distinctions and the laws with which 
they are connected. Now, here lies our great difficulty 
to-night. I cannot exhibit to you specimens of the 
objects about which I am to speak. I cannot bring a 
cirrus or a cumulus cloud into this room, and then 
proceed to examine or point out its peculiarities. Not 
only so, but I cannot refer you to any collection of 
specimens, labelled and ticketed and ready for your 


Clouds and Weather Signs. 107 

examination elsewhere. Not only so, again, but I can- 
not well refer you by way of illustration to special types 
of clouds depicted in the well-known paintings of the 
best artists. Even of those painters who devote much 
labour to their cloud studies, by far the greater number 
employ these only to produce what we call " atmospheric 
effects ;" and for this purpose the vaguest, least definite, 
and therefore least typical, cloud forms afford the 
materials most easy to handle. Neither can we blame 
the artist who reflects the mind or paints for the eye of 
the general public, to whom a cloud is a camel, weasel, 
or v/hale shaped mist, and nothing more. Again, I have 
not the cunning of the draughtsman's hand, and I cannot 
exhibit what I consider perfectly satisfactory drawings %\4j{jui 
of the most distinctive varieties, though I shall show you 
presently, by aid of the lantern, reproductions of some 
portraits of a few special types of cloud. Further again, 
there does not exist in the minds of observers gener- 
ally any very reliable classification at all. I have often 
found two fairly good observers looking at a cloud 
together to be divided as to the species to which it 
belonged. Lastly — and here I come to what I consider 
the most serious difficulty of all — the old nomenclature 
of cloud varieties is in itself unsatisfactory ; and it 
would be premature to attempt to remodel it at present. 
Luke Howard was a very minute and accurate observer ; 
but in his day the laws which regulate the movements of 
the atmosphere were not understood. The distinctions 
of cyclone and anticyclone, and the relation of wind and 
weather to the distribution of barometric pressures were 

io8 Meteorological Lcdzires. 

totally unknown. Now I shall hope to sho\^' you that 
these are elements with which the forms as well as 
movements of the clouds are intimately connected : and 
a classification which takes no account of this connection, 
fails in a very important point. Again, the laws of 
atmospheric electricity were not so well understood in 
Howard's days as in our own, and the behaviour of the 
clouds is evidently controlled to a great extent by this 
agent. Here, indeed, we are still extremely ignorant ; 
and until, by the use of captive balloons or other appli- 
ances, we have settled a number of hitherto unsolved 
questions about the electricity of the clouds, we must be 
content to wait, and not to adopt too hastily any new 
classification. The relation of the electrical states to 
evaporation and precipitation, on the one hand, and to 
the horizontal and vertical movements of the atmosphere, 
on the other, will one day be thoroughly understood. 
But until that day arrives, we can be neither too critical 
nor too cautious in our use of cloud classification. 

Amid these embarrassments we must steer our way 
as well as we can. With the existing nomenclature of 
the clouds I shall to-night tamper as little as I can help ; 
though I shall be forced every now and then to point 
out to you that in that nomenclature distinctions have 
been made where there are no natural differences, and 
what is at least as serious, that there are differences in 
nature where there are no distinctive appellations. 

Cloud forms have been regarded as naturally divisible 
into three great genera, the cirrus, the cumulus, and the 
stratus, A dual division would, perhaps, be as simple 

Clouds and Weather Signs. 109 

and as true. There are first the clouds which tend to 
arrange themselves in a horizontal bed or layer, the com- 
ponents of which may be either fibrous and interlacing 
(which is commonly noticeable when the bed is at a great 
elevation), or more compactly welded together (which 
is more common when the bed is near the earth's sur- 
face), but whose vertical diameter is in any case very 
small as compared with its horizontal. And there are, 
secondly, the clouds of massive spherical or hemispherical 
shapes ; often spherical or nearly so when in the higher 
regions of the atmosphere, but usually of the more hemi- 
spherical shape, and having a plane base, when in the 
inferior regions. These two great genera, however, are 
determined by form alone ; and they exist, though with 
various modifications (such as that I have just men- 
tioned), at all altitudes at which clouds are visible 
at all. Thus, at a vast height above the loftiest 
mountains and over the heads of the most adventurous 
aeronauts, the condensed vapour floats either in the thin 
reticulated sheet which produces our lunar or solar halos, 
or else in that flotilla of innumerable nubeculse which gives 
such a tranquil beauty to many of our summer skies. 
And as we descend towards the surface of the earth we 
find these two primary varieties quite as distinctly 
noticeable. Even the fogs which rest upon the earth 
itself have sometimes a plane upper surface, like the 
white mist which at nightfall clothes the valleys with a 
silver sheet, sometimes a mountainous superstructure of 
towering cloud, swelling upwards in billowy folds. 
The first of these divisions comprises essentially the 

I lo Meteorological Lectures. 

clouds of the night, and the second those of the 
day. Again, clouds of the first division are those of 
winter, those of the second, clouds of summer. But 
this rule applies with much fewer exceptions to the 
lower than it does to the higher portions of our atmo- 
sphere. Finally (but this rule again has many excep- 
tions), clouds of the first division are more common over 
the sea than over the land ; those of the second, more 
common over the land than over the sea. On the west 
coast of Norway, for example, I have often seen the 
mainland covered with massive piles of cumulus, while 
over the open sea were only a few streaks of linear cloud. 
Each little island had a little cumulus poised above it ; 
a larger island a larger cumulus, and so on, the size of 
the cloud being almost exactly proportional to that of 
the land surface beneath it. It is even said that a reef 
when covered with shallow water often has its position 
marked by a solitary cloud of the cumulus form above 
it. Now it would be convenient to base our nomencla- 
ture of clouds on this natural division, and this has, to 
some extent, been commonly done. Unfortunately, as 
I think, Howard almost restricted the term stratus, or at 
least primarily applied it, to ground-fog, although he 
applied its compounds to clouds of all altitudes. In 
the present Lecture I shall make bold freely to use the 
word stratus, as well as its derivatives, of clouds of what 
I have called the first division. The term cumulus and 
its derivatives we will apply to those of the second. 

The most valuable, however, of weather signs are 
obtained not so much from the shape of the clouds as 


Cjeog'^Bstab^ ZoTidoTv. 

Clouds and Weather Signs, 1 1 1 

from the directions from which clouds of different levels 
are observed to travel, and it is these weather signs, 
which, in the present state of our knowledge, can be 
most readily reduced to definite rules. From the use 
of synchronous weather maps there has sprung up in 
recent years a new science of the winds. With the 
principles of this science all the more reliable rules of 
weather forecasting are most intimately connected. We 
no longer think of judging of coming weather merely 
by the aspect of the sky and an examination of an in- 
dividual barometer. We invariably refer — I do not say 
to the weather reports of a few hours previous, for we 
often have neither these nor any weather reports at all 
at hand — but we invariably refer to rules already de- 
duced from the long study of weather maps. The man 
who ignores these rules had better, in my opinion, leave 
all attempts at weather forecasting alone. At best his 
weather lore will not rise much above that of the bees, 
which fly to the hive, often to their own detriment, 
whenever a dark cloud covers the sun. When to take, 
and when not to take, an umbrella is a question which 
involves at least an elementary knowledge of the rela- 
tions of pressure and winds, of the general direction and 
interdependence of cyclone and anticyclone, in short, 
of the matter with which the meteorological services 
of this and other countries supply us. Now the move- 
ments of those clouds, which are at the greatest distance 
from the earth's surface, afford to the observer informa- 
tion of the highest value concerning the distribution and 
movement of the areas of barometric pressure existing 

1 1 2 Metco7'ological Lectures. 

at the time when he makes his observations. I am 
going to give you a few rules upon this subject. But 
we must first settle one point with regard to nomencla- 
ture. It is absolutely necessary that we should have 
some one term to designate unequivocally this highest 
class of clouds. We will employ then the term cirrus, 
and its compounds cirro-stratus and cirro-cumulus, but 
these terms, if our rules are to hold water at all, must 
be restricted to clouds of the greatest elevation. Owing 
to the fact already mentioned, that the term stratus has 
been applied to ground fog, observers have used its 
compound cirro-stratus of a great variety of clouds of 
all altitudes, and to the loose application of this word in 
meteorological reports and weather diaries is due, in 
great measure, the small amount of progress hitherto 
made in our knowledge of the upper currents. At one 
time the observer gives the name cirro-stratus to that 
filmy sheet of very elevated cloud which produces the 
halo ; at another to streaks of linear cloud at not half 
that elevation ; and finally, to make confusion worse 
confounded, the older observers tell us that even some 
of our fogs, I suppose frozen fogs, are "a species of 
cirro-strati." Further confusion, arising from the use of 
another term, which I must touch upon presently, hangs 
round the ordinary use of the word cirro-cumulus. In 
what I say to-night I employ the word cirrus only of 
those " curl clouds " or " mares' tails," which float at a 
great elevation (see Fig. i). By cirro-stratus I mean 
the halo-producing sheet, which is formed by the inter- 
lacing fibres of more or less cirriform cloud. And finally. 

ClotLcis and Weathei'- Signs. 1 1 3 

by cirro-cumulus, I mean those small white nubecules 
which float in the same level as the cirrus and cirro- 
stratus. I call these three descriptions of clouds gener- 
ally, clouds of the cirrus class, and the currents which 
carry them I denominate simply upper currents. 

Now the laws which govern the upper currents and 
their clouds are to some, though not to a very great 
extent, already understood. They are complex, and I 
should go beyond the sphere of this Lecture if I at- 
tempted to explain all that is known of them to you 
now, but I think I can tell you enough of them to be 
practically useful in forecasting probable changes of 

You all know that the winds at the earth's surface ^, ^ 
blow round any area of low barometer, which is also, 
generally speaking, an area of wet or showery weather, 
and that they blow in such a way as to have the place 
of lowest barometer considerably on the left (in our 
hemisphere) of their course. You have also heard that 
the depressions, or areas of low barometer, commonly 
travel fro m S.W. to N.E ., or at least from some southerly 
or westerly to some northerly or easterly point. Like- 
wise, that the majority of the centres of these depressions, 
around which the winds blow in cyclonic circulations, 
pass along on the N. or N.W. of this, and indeed of any 
part of the British Isles, while others travel directly over 
us, and some again leave us on their N.W. You also 
know that, besides these areas of low pressure, there are 
areas of high, anticyclones, as they are called, in which 
the weather is commonly dry. These latter are, com- 


114 Meteo7'ological Lecttires. 

paratively speaking, stationary often for a considerable 
time, and their disposition seems to affect the movement 
or translation of the areas of low pressure, which com- 
monly so travel as to have the anticyclone on the right 
of their course. 

Now the old observers were quite right in telling us 
that we know a great deal about coming weather from 
the appearances and forms of the clouds. They com- 
paratively neglected the prognostics to be obtained from 
the movements of those bodies. We must give our at- 
tention both to form and movement, but more especially 
to the latter, in judging of the disposition of the areas 
of high and low pressure. 

If, when a light breeze from the south is blowing at 
the earth's surface, while clouds of various altitudes are 
passing overhead, you study with care the motion of 
these clouds, you will in general observe that their 
course makes a considerable angle with that of the 
surface wind, and that if your back is turned to the latter 
the clouds travel somewhat from your left hand to your 
right. Low scud will probably be seen to travel from 
S. by \V. ; stratus at a higher level from S.W., while the 
threads of cirrus, or fragments of cirro-cumulus, at 
a still higher level, move from a still more westerly 
point. Draw every day, when clouds of the cirrus type 
are visible, a dotted arrow indicating their motion on 
one of the daily weather charts, and you will find that, 
as a rule, the upper currents flow considerably across the 
isobars, and their motion is, on the whole, from the 
districts of low barometer towards those of hio^h. You 

Clouds and Weather Signs. 1 1 5 

will find some singular exceptions to this rule, but of its 
general accuracy you will not be long in convincing 
yourselves. Now at the earth's surface the winds do not 
blow exactly parallel to the isobars, but in such a direc- 
tion as to carry a portion of air from the districts in 
which the pressure of the atmosphere is high into those in 
which it is low ; and it is therefore obvious that the air 
which thus finds its way into the regions of depression, 
there rises and escapes again above, eventually finding its 
way to the anticyclones, where it again descends towards 
the earth's surface. From an examination of instances of 
upper currents, it has been found that the upper current 
makes a mean angle of as much as 55° with the surface 
wind in our district of the globe. This angle is, however, 
far from uniform in the different portions of the cyclonic 
and anticyclonic areas. I will try to explain how the 
upper currents move under special but common circum- 
stances, describing at the same time, as briefly as I can, 
the general aspect of the clouds prevailing in these 

There commonly exists in the front of an advancing 
barometric depression a great bank of the frozen moisture 
in the high regions of the atmosphere which we call 
cirro-stratus (see Diagram). Synchronous observations 
show that the edge of this bank is commonly curved ; and 
that the curve is, roughly speaking, a parabola, the focus 
of which lies nearly in the line along which the centre of 
the depression is about to travel. We do not, however, 
commonly see this curve in looking at the cloud. What 
we do see are longitudinal threads, or filaments of thin 

; 1 1 6 Meteorological Lectures. 

cloud, at an altitude of between 25,000 and 40,000 
feet above the earth, and so arranged as to be parallel 
to each other. Outlying streaks of this cloud, often 
from 20 to 100 miles in advance of the main pack, the 
pioneers of the coming army, can be examined without 
difficulty, and their general appearance is so well known 
that I need not describe it minutely to you. Suffice it 
to say that these threads of ice crystals terminate in most 
attenuated points, which are often curled more or less 
outwards or upwards, being apparently kept asunder by 
electrical repulsion, the whole thread acting as a hori- 
zontal conductor of electricity. As the actual bank 
comes over us the threads which compose it are seen to 
be more or less reticulated, forming a filmy sheet or 
canopy, the structure of which becomes less and less 
discernible. This is the form of cloud which produces 
our halos. Occasionally, indeed, even from the very first 
appearance of this sheet, we can scarcely discern any 
structure in it at all ; the sky seems simply to become 
gradually overspread with a milky-looking film of whitish 
cloud matter. In this latter case we infer that the 
upper regions are especially humid, and that the crystals 
being less insulated consequently do not arrange them- 
selves in definite threads. 

In any case, as the bank comes more fully over our 
station, its under surface becomes lower, and is at the 
same time rendered indistinct by the formation of visible 
cloud matter in the lower regions of the atmosphere. 
The commencement of this stage usually coincides with 
that of the fall in the mercurial column : for the 

Clouds and Weather Signs. 1 1 7 

barometer is often either rising or stationary under the 
outlying threads already described. The rain-bringing 
wind now begins slowly to make itself felt at the earth's 
surface ; the upper clouds cease to be visible at all, for 
the sky becomes totally covered by a composite mass of 
condensed vapour, and more or less precipitation at once 
sets in. When it clears again we shall have totally new 
conditions to examine. But while we are kept indoors, 
and have nothing particular to look at, let me go back 
and describe to you, as briefly and clearly as I can, what 
have been the movements of that upper current which 
has brought this cloudy canopy over our heads. 

I have spoken of electricity as apparently determin- 
ing to some extent the form of the cirrose filaments. 
Some writers have gone so far as to suppose that their 
motion through the sky is due to the same agent, raising 
the latter to the throne of "the cloud- compelling Zeus," 
who controls all the movements of the ice-mist. 
Observation, however, rejects the too ambitious claims of 
this potentate, and will soon satisfy any one that the. 
movements of these clouds are controlled by winds, due 
to differences of pressure in the stratum where they 
float. Synchronous observations, made at difierent 
stations, carry us a great deal further, for they indicate 
the laws by which these upper currents are governed. 
I must not here attempt to describe to you those laws ; 
but I must beg your attention while I describe some of 
the general rules which depend upon them, rules which 
he who wishes to be weather-wise will very frequently 
have to employ. 

1 1 8 Meteorological Lectit7'es. 

I will suppose then, first, that depressions are travel- 
ling from S.W. to N.E. (which is with us their most 
common direction), an anticyclone lying to the S.E. of 
our district. First, let us imagine ourselves to be situated 
actually upon the line which is to be traversed by the 
centre of the disturbance. Cirrus threads will first 
appear upon the S.W. horizon, and parallel to^ that 
horizon. Their motion can then be made out, though 
not very exactly, like that of any other moving body 
at a distance. When some of them have arrived at the 
zenith we shall find them to travel from some point 
between W.S.W. and W.N.W. (see Fig. 2). A little later, 
when an easterly wind has sprung up beneath, and when 
the cloud-bank is getting thick, we shall, if we can catch 
an opportunity of seeing the higher clouds, find that their 
current has " backed," that is to say, is now from a rather 
more southerly point. By and by, when the barometer 
has reached, or nearly reached, its minimum, if we have, 
as we probably shall have, an opportunity of going out 
again to witness the clearing of the sky, we shall find 
that this upper current has backed so much as to be 
then moving from a south-easterly point. The cirri 

^ Here, and presently, I employ the words "parallel to" a particular 
horizon, as expressing, briefly but intelligibly, parallel to the tangent of, or 
to a line which subtends, a particular arc of the circle of the visible 

Apparently, i.e. as seen on the vault of the sky, the bands and banks 
of Cirrus are arched. Thus a band seen on the S.W. horizon is seen as 
most elevated in its middle part, viz. in the S.W., and lowest at its 
extremes. The observer must of course not confound this apparent curve 
with the real curve (shown in a cloud-map, or in the diagram), which I 
have previously stated to be rarely visible to the eye, in looking at the sky. 

Clouds and Weather Signs. 1 1 9 

will then be ranged in lines from S.E. to N.W. Their 
appearance will at the same time have greatly altered ; 
they will have become much more massive, and their 
threads or tufts will commonly be seen to point in a 
more or less downward direction, indicating that a cold 
and drier atmosphere is setting in below (Fig. 3). 

Now let us shift our position, or that of the advan- 
cing depression, and imagine that the latter, in this case 
also travelling from S.W. to N.E., is passing considerably 
to the N.W. side of our station ; say, is passing along the 
N. of Scotland while we are in London. In this case 
the bank of cirro-stratus, or its out-lying threads, have 
first been visible on the W. or W.N.W. horizon, and 
parallel to that horizon, and the upper-current, when it 
can be observed, is found to travel from some north- 
westerly point. As the bank spreads over us, while the 
south-westerly wind springs up beneath, we observe the 
upper clouds to be less thick and watery looking than 
in the description I have given before. Cirro-cumulus 
often takes in this instance the place of cirro-stratus, 
which is probably an indication that no great conduction 
of electricity is going on aloft. The rain, if it reaches us 
at all, falls in spasmodic showers. And when the sky 
clears, we shall find that it does so far more gradually 
than is the case at stations nearer to the centre of the 
disturbance. Here, too, we shall find that the upper 
current has backed, but only to a W. or S.W. point, so 
that when the wind at the earth's surface has veered to 
W., clouds of every level over our heads will be found 
to move from nearly the same quarter. 

1 20 JMctcorolog ical L cchires. 

Once more I must trouble you to imagine our cir- 
cumstances changed. A depression, still going in a 
north-eastward direction, is leaving us upon its left : is 
travelling, we will say, from the Bay of Biscay to Holland 
and Denmark, while we are in London. In this instance 
the cirro-stratus bank first shows itself on the S.S.W. 
horizon ; and its motion, when it can be first determined, 
is from some point between W.S.W. and S. In this 
case, after the sky has thickened, and a north-easterly 
wind has freshened, with a falling glass, we very rarely 
get an opportunity of seeing the upper clouds at all : 
but when we do, at the time that the centre of the dis- 
turbance is nearest to us, we usually observe the upper 
current to have backed so as to come from S.E. The 
rain, in this instance, if it extends so far N. as our station, 
is cold, thick, and continuous. As it ceases the clouds 
remain for a little while low and dreary ; the clearing of 
the sky is very gradual, and when the wind is gone round 
to N. and the barometer is rising, we commonly see that 
the main vapour plane has greatly descended, and that in 
lieu of the cirrus, cumulus, and shower-clouds which are 
being experienced in the far south, we have irregular but 
level stratus occupying the middle or rather lower beds 
of the atmosphere. 

We must shift our position, please, once more, and 
suppose ourselves to be altogether in the rear of a dis- 
turbance, the central part of which has passed fairly off 
to the N.E. My task of description is here comparatively 
easy. The sky is either clear or contains fragmentary 
cumulus, and perhaps a few local shower-clouds. Such 

Clouds and Weat/ic?" Signs. 121 

upper clouds as are seen are here commonly either 
masses or threads of somewhat curly cirrus ; if threads 
they stretch from N.W. to S.E., and their motion is in 
any case nearly from that direction, and thus coincides 
or nearly so with the line of the isobars, and with the 
winds at the earth's surface. It is a very rare thing to 
experience a N.W. wind (except immediately after it 
has veered to that point), which does not extend to the 
highest regions of the cloud-bearing atmosphere. 

Now you are probably aware that when depressions 
are passing over or near us, the general distribution of 
high and low barometer is not always such as I have 
been describing in the last ten minutes. A great 
anticyclone may be lying to our east, and depressions 
may be for some time travelhng northwards ; or, again, it 
may lie on our west, and depressions may be going south- 
eastward. You may be afraid that I am going to give a 
new set of rules for these conditions as lengthy as those in 
which I have already indulged. Fortunately for you I 
need do nothing of the kind. We have only got, in the 
first instance, to back, if I may be allowed the expression, 
all the words that I have used, S.W., N.W., etc., as much 
as four points, i.e. to S., W., etc., or, as I now do, to alter 
the position of our diagram, and the rules which I have 
already given will still be true. In the latter instance, 
namely, if the depressions are going S.E., we must 
veer our words as much as eight points, or shift our 
diagram, as I now do, and our rules will be as useful as 
before. I shall give one or two practical illustrations of 
what I mean. In weather in which we know, from the 

122 Meteorological Lectures. 

previous changes of wind, and, better still, from our study 
of the daily maps, that the depressions, or areas of rainy 
weather, are travelling from S. to N., the appearance of 
a thick bank of cirro-stratus in the S.E., moving from 
some point between S.W. and S. after an interval of fine 
weather, is often an indication of coming rain, probably 
heavy, and accompanied by a muggy N.E. wind. On 
the other hand, if, under the same circumstances, the first 
threads of cirrus or cirro-stratus are observ^ed in the 
W., but are found to travel from the S.W., the rainfall 
is not likely to reach our station, at least in more than 
one or two passing showers. 

Again, let the weather be such as we frequently have 
in spring, and occasionally in autumn and winter, winds 
backing and veering between W.S.W. and N., and the 
weather maps showing us that areas of bad weather are 
travelling from the Scottish coasts towards Holland and 
Denmark. Let a fine day be succeeded by a watery 
bank of cirro-stratus in the N.W., travelling from the 
N. or N.N.E. ; bad weather is to be expected ; a blustering 
westerly wind accompanied by composite cloud-bank 
will probably veer to a cold N. or N.E. gale, a hazardous 
time for the shipping on our N.E. coast. On the other 
hand, under the same circumstances, let the cirrus appear 
first in the N.N.E, and travel from a northerly point, 
we are not then likely to experience more than a few 
slight showers of sleet or snow, with only a moderate 
backing and veering of the wind. 

I must not dwell longer on the motions of the cirrus 
clouds round our depressions. I hope that what I have 

Clouds and Weather Signs. 123 

said has tended to show you that the whole subject is 
one of great importance in making forecasts of the 
weather, and in judging of the probabihties of storms ; 
and I shall be glad indeed if I have induced any of you 
to enter upon this class of observations as a study. You 
will have, in this case, many difficulties to get over, especi- 
ally those to which I have already alluded, arising from 
the labour of training the eyes, but I can assure you 
that the pleasure and interest of the study, as well as its 
practical utility, will be the ample reward of perseverance. 
I have already several times spoken of local showers, 
and must have seemed to pass them over as of little 
account. Now a temporary shower is often quite as 
important a matter, to the agriculturist, for example, or 
to the pleasure-seeker, as a steady downfall of rain ; just 
as a squall is often a more formidable matter to a sailor 
than a gale. Moreover, to judge of the chances of the 
passing shower or squall, is a more difficult task, to 
ordinary observers, than to prognosticate more con- 
tinuous bad weather. Here, again, we must first allude 
to a matter of phraseology. Howard, the cloud classifier 
and cloud classic, called every form of cloud from which 
rain falls by the name nimbus. In the Latin definition 
which he gives of this name, he does appear to indicate 
a twofold division of nimbi or rain clouds ; but neither 
he nor his successors have told us very much about this 
division. I have shown you that the symptoms of the 
extensive rainfalls become first apparent, as a general 
rule, in the higher regions of our atmosphere ; the cloud- 
bank begins at a high level, and is succeeded by com- 

124 Meteorological L cc lures. 

posite cloud at a lower level. The formation of passing 
showers is commonly the converse of this process. I 
must briefly describe that formation, familiar as it is to 
most observers. Almost every one must have watched 
the formation of a cumulus cloud, probably in the earlier 
hours of a showery day. Loose shreds of irregular cloud 
matterbegin to appear hereandthereunderthebrightblue. 
They are at first near the earth's surface, commonly in 
what has been the vapour plane of some stratus in the 
preceding night. Gradually, as rapid evaporation goes on 
under the increasing power of the sun's rays, the rising 
vapour forces upward the particles above it, which are 
condensed by the cold of the higher regions into more and 
more mountainous masses. The under surface remains 
level, reposing on the vapour plane, that is, precisely at 
that altitude above the earth at which water passes from 
the gaseous state to that of mist. Below the cumulus the 
vapour is rising, but in the invisible state, like the steam 
out of the funnel of a locomotive, which is often invisible 
until it has risen a foot or more above the aperture. Look- 
ing aloft, we see the general shape of the cumulus to be, 
as I have described it before, that of a hemisphere, or 
possibly of a cone. It is not, however, smooth, but still 
resembles the steam-cloud of the locomotive in exhibit- 
ing rounded protuberances. If you look at these you 
often see them continually tumbling back into the main 
body of the cloud, which yet continues to swell gradu- 
ally upwards and outwards. That the older meteorolo- 
gists were right in attributing this process principally to 
electric disturbance I, for my part, cannot doubt. The 

Clouds and Weather Sigjis. 1 2 5 

cloud is now an insulated body more or less highly- 
charged. It repels the opposite electricity from the 
particles in its neighbourhood, and attracts them to 
itself, and an invisible rain of such particles is per- 
petually pouring probably upon all parts of its surface, 
the general charge of the cloud being retained partly 
by reason of its spherical surface. While we have been 
watching our cloud many others of similar structure 
have formed in other parts of the heaven, and our 
attention is attracted towards the horiz®n by the roll of 
the first distant thunder clap. We see in the quarter 
from which it has proceeded a cumulus or body of cumuli, 
the upper surface of which has put on quite a different 
appearance. It is spreading outwards and upwards in 
very thin cirrus-like filaments (Fig. 4). It has, in 
fact, risen to such a height as to approach a stratum of 
gas intensely electrified, and with an electricity opposite 
to its own, and it is disposing the ice prisms in 
innumerable threads or feelers, spreading their attenu- 
ated points through the lofty regions of highly rarefied 
air. We look again at the cumulus which we have 
watched before. Its glowing summit is undergoing a 
similar metamorphosis, becoming softer and more downy 
than the lower portions of the cloud. Exactly at the 
same time that this change is taking place we notice 
the atmosphere beneath our cloud to begin to be dimmed 
by the falling rain. The neutralisation of the electricities 
aloft has permitted the particles of water, hitherto kept 
asunder by repulsion, to unite and be discharged to the 
earth in ever-swelling drops. By and by little will be 

126 Meteorological Lectures. 

seen of the melting cloud save a certain amount of 
cirrus disposed above, and some loose flecks of scud, or 
of soft cumulus beneath. 

This is the first formation of the typical shower ; and 
it is a great pity that we should possess no title serving 
to distinguish this formation from its opposite, that of 
the more wide spread nimbus. You do not always see 
the process of development which I have described. We 
have showers and showers ; showers which have been 
formed a long way off, and are carried by the winds 
over our heads before they have dispersed, and showers, 
too, which are so imbedded in other cloud forms that we 
fail to get a glimpse of their cirri-form summits, or even 
to distinguish the outline of their sides or base. Showers 
of thick small rain even fall, in some circumstances, 
from low clouds of the stratus type, but these clouds 
also, just before their precipitation commences, lose their 
definiteness of outline as regards their upper surface, 
always looking as if they were discharging rain or snow 
in an upward, as well as in a downward, direction. But 
the formation that I have described is decidedly that 
most distinctive of the local shower, in contrast to the 
wide spread rain. 

Now we all know that the first steps of the formation 
which I have described are often discernible without 
being followed by any shower at all. In fine weather, 
especially in the spring and summer, we often see 
cumulus forming day after day, attaining its greatest 
dimensions about the hour of highest temperature, and 
either dissolving altogether about sunset, or subsiding 

Clouds and Weather Signs. 127 

into the loose spread stratus which is scattered at night- 
fall through the vapour plane. I must give you a few 
rough and ready rules which may be some assistance in 
judging of the probability or otherwise of passing 

First of all then, I would say, look to your barometer, 
and to the indications which it affords in connection 
with the quarter of the wind. Most of our showers are 
related to areas of depression existing over us or in our 
neighbourhood. We shall therefore rarely expect them 
when the barometer is very high, say much above 30 inches 
at sea level. Again, we have seen that passing showers 
are especially numerous on the right hand side and in 
the rear of a depression. Consequently, we shall be led 
to expect them when the wind is veering or seems likely 
to veer, and when the barometer is rising or seems 
likely to rise. Next you may study with some advan- 
tage the colours of the sky and of the landscape. 
These are, indeed, in many instances, more closely 
related to the advance or retreat of the extensive 
nimbus, forjudging of the probabilities of which I have 
already given you what I consider more dependable 
rules. For example, a red dawn is commonly taken as 
a sign of bad weather, and the inference has of course 
a basis in fact. In the evening the minute particles of 
water, together with dust, suspended in the air, usually 
cause light, transmitted through a long stratum of this 
air, to be red. During the night a great number of these 
particles are deposited on the earth's surface. If after 
the precipitation in dew, the rays of the rising sun 

12 8 Meteo7'ological Lectures. 

appear red, we conclude that the air still carries numer- 
ous water particles which, after the morning evaporation 
and the diurnal rise of the vapour plane, are likely to 
form rain-clouds. A grey or yellow sky in the evening 
is usually due to much cloud matter in the west, especi- 
ally in the form of cirrus or cirro-stratus, stopping the 
direct rays of the sun, or a considerable portion of them. 

"Visibility," or the remarkable distinctness of distant 
objects, is, on the other hand, another popular prognostic 
of rain. It is no doubt, to some extent, the effect of 
previous rains, the precipitation having washed the at- 
mosphere of its dust, either in the district where the 
visibility is observed, or in that which lies to the Avind- 
ward of it. Unusual refraction is, I think, a more trust- 
worthy sign, indicating that the rays which reach the 
eye have passed through closely contiguous strata of 
air of varying densities, the commingling of which is 
likely to produce precipitation. But these and other 
such like signs are inferior to those which we derive 
from a minute study of the cloud forms. 

When cumulus begins to form under those other cir- 
cumstances which lead us to suspect coming showers, 
watch its formation and appearance with great care. A 
very rapid upward development of the cloud, while the 
outline is hard and the base very level, is a bad sign ; 
which is intensified if the protuberances of the upper sur- 
face are seen to toss and roll with much activity. When, 
as is very commonly the case, there are clouds of other 
species in the sky, notice these particularly. If there is 
a good deal of loose stratus, the remains of night-cloud. 

Clottds a7id Weather Signs. 129 

around the base of the cumuli, and the latter are forcing 
their domes far above these, and gradually absorbing 
or repelling them beneath, the occurrence of showers 
before nightfall is probable. On the other hand, if 
there is stratus at a moderate altitude, and cumuli are 
formed still lower down, and the summits of the latter 
seem inclined to spread out and blend with the stratus 
as they reach it, while the bases of the cumuli become 
ill-defined, and appear gradually melting, the weather is 
pretty sure to remain dry. In the latter case there is a 
sort of second cloud-plane in the middle region of the 
atmosphere, namely that occupied by the stratus, which 
serves both to impede the evaporation from the earth's 
surface by checking the solar rays, and also to conduct 
horizontally the electricities of the clouds, at a very early 
stage of their formation. On the left hand of the picture 
which you now see (Fig. 5), you have a likeness of one 
of these quiet and well-intentioned cumuli. The stratus 
in this particular instance is of a special kind, never, or 
hardly ever, seen before rain, which has received, I be- 
lieve, the title of " rolled-cumulus," though I do not call 
it cumulus at all. On the right hand side of the picture 
I have given, by way of contrast, the bold level-based 
cumulus, which is often the precursor of a hail or thunder 
shower ; a handsome, but rakish and suspicious charac- 
ter, whose proceedings you should watch with some care. 
By and by he will probably begin to assume his tufted 
crown, " foenum habet in cornu " — to misquote a Latin 
poet — "hunc tu Romane caveto" — put on thy water- 
proof, O Briton. 


I ^ o Meteorological L ectures 

It is a very common thing, on those occasions when 
there is what I have called a second cloud-plane at no 
very great altitude, to see cumulus, when its summit 
reaches this plane, spreading out in very thick opaque 
folds, so that the cloud altogether may be in shape com- 
pared to a mushroom with a very thick stem. To the 
inexperienced eye these clouds have a somewhat stormy 
and formidable appearance, probably because they are 
rather similar in shape to those far loftier shower-clouds, 
whose summits have spread outwards into the cirrus 
regions of the atmosphere, and the untrained eye recog- 
nises form far more readily than distance. Yet clouds 
of the kind I am nov.' speaking of rarely or never pro- 
duce a shower. They may be seen at all times of the 
year, but especially in spring, particularly in the south- 
eastern "parts of an anticyclone. They are most com- 
monly accompanied with a good deal of haze, and 
associated with a dry and harsh atmosphere. One 
might almost suppose, from parts of his description, that 
these clouds are what Luke Howard intended to de- 
signate as cumulo-stratus ; but other remarks which 
both he, Forster, and others make about the cumulo- 
stratus, show that they intended by this term to desig- 
nate the cirrus-crowned cumulus, which I have spoken 
of to-night simply as the shower-cloud. There are 
other and later representations of cumulo-stratus, ac- 
cording to which this title ought to be given to ordinary 
cumulus co-existing in the sky with a good deal of 
stratus. As stated before, I am not attempting to 
reform the nomenclature of the clouds, being concerned 

Clotids and Weather Signs. 131 

with the things, and only incidentally with the names, 
and therefore shall not dwell upon this point further. 

The mention, however, of cumulo-stratus leads me 
to ask your permission to introduce to you an especial 
favourite of my own, who comes with no credentials, 
and is, in fact, a sort of innominato. It is not simply a 
cumulus co-existing with stratus, but a true hybrid 
between cumulus and stratus, to which I only wish the 
name cumulo-stratus had been given. Of all the clouds 
that ever adorn our English skies there are few which I 
think more elegant, and there are none so distinctive of 
special, though rather uncommon, types of weather, as 
the one of which I am going to speak now. I have tried 
to picture for you, as you see (Fig. 6), some of these 
clouds, but I could not with exact fidelity represent either 
the uncontrolled irregularity of outline, or the exquisite 
delicacy of reflected lights which are manifested by 
these clouds when scattered over the sky. I may 
describe them, in general, as very high stratus, having 
numerous turrets or protuberances emanating from its 
upper surface. They would, by many, be denominated 
cirro-cumuli, but there is really nothing of the cirrus 
about them. From observations of the shadows thrown 
by these clouds, I have found their altitude to be rarely 
less than 14,000 feet. They therefore almost belong to 
that class which may be defined as upper current clouds. 
In direction of movement they are commonly inter- 
mediate between the cirrus-current and the surface- 
wind, but are much nearer to the former. The pe- 
culiarities of this type of cloud are as follow : — They 

132 Meteorological Lectui^es. 

hardly ever occur in our islands, except in summer, 
and rarely then, unless the temperature is above the 
mean. They are rather more prevalent in the inland 
districts than elsewhere, and they are, I believe, least 
common on the Atlantic coast, and especially uncommon 
on the west coast of Ireland. They are usually seen near 
the western and south-western limits of an anticyclone, 
when there happen to be one or more shallow depres- 
sions to the southward, that is over the Channel, France, 
or the Bay of Biscay. They seem to be associated with 
vast electrical disturbances in the higher regions of the 
atmosphere, and they are very commonly the precursors 
of our grandest thunderstorms. This is especially the 
case when they move with great velocity from a south- 
easterly or southerly point, while clouds a little below 
them are flying from N.E. or E. Under these circum- 
stances, a single fragment of cloud of the type I am 
describing, however minute, occurring in a bright sky, 
and perhaps with a high and steady barometer, will 
sometimes enable the accurate obsers^er to prognosticate 
thunder with a success which is astonishing to those 
unacquainted with his secret. These clouds sometimes 
disappear before the occurrence of a thunderstorm ; the 
latter then takes place in the day time, and is formed 
from the cumulus type already described. But there is 
a remarkable class of thunderstorms which come on with 
the clouds of which we are now speaking. This cloud 
resembles ordinary stratus in one respect, that it glories in 
the night. Soon after sunset on a summer evening it often 
thickens and darkens in the S. and S.W., its under surface 

Clouds and Weather Signs. 133 

being disposed in numberless wave-like folds, through 
which, here and there, shine the highly reflecting sides of 
its broken but cumulus-like turrets. Presently the sheet 
lightning begins to illumine the southern sky, while 
a light easterly or northerly breeze is felt below. In a 
few hours the storm is raging in its might, a magnificent 
display of celestial fireworks, remarkably unproductive 
of any disastrous effects, and in this respect standing in 
marked contrast to the thunder-showers whose base is 
at a lower level, and which are first developed from 
clouds of the ordinary cumulus type. Those of our 
summer thunderstorms which occur during the night 
are, with very rare exceptions, of the sort which I have 
now described. You are not to suppose that the kind 
of clouds which I am speaking of undergo no change 
when passing into the form which produces the shower. 
Their behaviour is analogous to that of the ordinary 
shower-producing cumuli. Their summits run up so 
as to inosculate, in some cases, with cirrus at no great 
distance above them ; in other cases those summits 
become spontaneously cirriform ; and this change, pro- 
bably accompanied by a neutralisation of electricities, 
is, so far as I have observed, and I have watched them 
through many a night, the essential requisite of their 
precipitation in rain. 

You will observe that I have spoken principally in 
this Lecture of clouds as prognostics of rain rather than 
of fine weather. I may be forgiven for doing so in a 
climate in which, grumblers say, it is always safe to 
foretell rain ; but in attempting to describe the rain- 

134 Metcoj'ological Lectures. 

bringing clouds I have to some extent implied that the 
opposite types are, relatively speaking, signs of fine 
weather. But I must, before I conclude, say a few 
words on one type of cloud, the occurrence of which is 
especially a sign that no rain is immediately to be 
expected. The anticyclones, or areas of high barometer, 
are, as already mentioned, in a general way areas of 
fine and settled weather. In summer we commonly 
see within these areas almost cloudless skies. A little 
stratus occurs at night on some occasions, at an eleva- 
tion of from 4,000 to 10,000 feet, and this is developed 
into cumulus of moderate dimensions during the day, 
while the unwashed atmosphere is usually slightly 
obscured by the haze produced from smoke and dust. 
At a great elevation cirrus may often be seen in comoid 
tufts, whose movement is extremely slow. In winter, on 
the other hand, neither cumulus nor cirrus is common 
near the central parts of an anticyclone ; but the sky is 
rarely clear. A bed of nearly stationary stratus often 
covers the heavens for many days and nights in succes- 
sion. This bed is frequently of vast extent, but of very 
small vertical thickness. Where gaps occur in it, such 
as that which I have tried to portray in the illustration 
which you now see (Fig. 7), we observe a sky totally 
devoid of every species of upper cloud. Now we infer, 
from facts which I cannot stay to describe to you now, 
that there is over every anticyclonic area a slight 
general downward movement of the atmosphere. In 
the summer the sun's rays dissolve the stratus, and the 
rapid evaporation taking place during the long and hot 

Clouds and Weather Signs. 135 

days sends up the local or scattered patches of cumulus 
or cirrus. In winter this does not take place. The 
vapour in the very high regions of the atmosphere is 
carried by the descending current towards the surface 
of the earth ; it therefore probably experiences a rise of 
temperature, and, consequently, does not pass from the 
gaseous into the visible form. The surface of the earth 
is, however, losing heat by radiation, and at an altitude 
of about 3,000 feet or less (often much less) above that 
surface a temperature is encountered which is low enough 
to condense the gas into a level sheet of vapour. The 
remarkable continuity of this sheet I imagine to be due 
to the fact that wherever a break in it occurs the earth 
consequently loses more heat by radiation, as our ther- 
mometers in such circumstances abundantly show, and 
the sheet is consequently speedily reformed. You must 
not suppose that beneath this bed of stratus the atmo- 
sphere is always as clear as it is represented in this 
picture. It is so sometimes, but occasionally over a great 
expanse of country, and especially in the neighbourhood 
of our large towns, the atmosphere is obscured by thick 
fog ; and the densest and darkest fogs which you experi- 
ence in London are commonly those which occur beneath 
the " anticyclonic stratus " which I have been describing ; 
these fogs being possibly due not only to the want of 
horizontal motion in the air, but partly also to the 
descending currents which accelerate the downward 
movement of the now water-laden particles of smoke. 

It is remarkable that although strati-formed clouds 
are in general more characteristic of the sea than of the 

136 Meteorological Lectures. 

land, the stratus which I am speaking of is much more 
continuous over the land than over the sea. It is also 
noticeable that the breaking up of one of these banks 
of stratus is usually the first sign of a change from 
settled to unsettled weather. The explanation which 
I have attempted of the manner in which the stratus 
bank is formed, helps us to interpret both these facts. 
The relative warmth of the atmosphere over the sea in 
winter prevents the formation of the stratus. And, 
again, the cessation of the general descending current, 
or the commencement of ascending currents, necessarily 
attends the breaking up or the passing off of the anti- 

My subject has no limits, and you must be aware 
that I have selected to-night only a few, a very few, of 
the points of interest which it embraces. If I have 
taxed your patience you will, I hope, forgive me. If, in 
making my selection, I have served in any degree to 
direct your attention to, or to enliven your interest in, 
a marvellously neglected branch of study, I shall have 
done all that I could hope to do in an hour's lecture. 
In any case you will permit me to conclude with the 
expression of my hope that before some of us may lie 
the not impossible task of elaborating, by ceaseless and 
minute observation, the materials of a science of 
nephology yet unborn ; and that to all of us may belong 
the opportunity of adding something to the enjoyment 
of life by a more watchful study of some of the least 
known, but most exquisitely delicate, of the operations 
of mighty Nature. 

S^^ ^-^v!Si^ 



What it is. — We are very desirous that there 
should not be any needless repetition in the present 
course of Lectures. Therefore, as my friend Dr. Mann 
described somewhat fully the conditions under which 
water exists in the atmosphere, I am at liberty to 
dismiss the first three words in my syllabus very briefly, 
and I might do so in the four words — Rain is condensed 
vapour. But in case any one is now present who was 
unable to attend the first Lecture, I will amplify slightly. 
The atmosphere consists of oxygen, nitrogen, dust, and 
sundries, all which are classed as dry air, and also of a 
variable quantity of water in the state of vapour. The 
hotter the air the more vapour it can contain, and this 
capacity of the air for moisture increases at an increas- 
ing rate, so that if you mix together a cubic foot of 
saturated air at 92°, and another at 32°, they would 
have a mean temperature of 62°, but the vapour tenable 
at 92° is 157 grains, at 32° is 2*i, therefore our 2 
cubic feet would contain lyS grains, or an average of 
8-9, but at the temperature of the mixture the air can 
contain only &2 grains, therefore the excess of 27 
grains must fall as rain. 

138 Mdeoi'ological Lectttres. 

Where it comes from. — This question might also 
be answered as regards this country in three words — 
the West Indies ; but further details are necessary. 
Some one, I think it was the late Commander Maury, 
likened the atmosphere to a steam-engine, whereof the 
tropical oceans were the boilers, and the temperate 
zones and the mountain-tops generally were the con- 
densers. This is nearly true, the vertical sun raises 
large tracts of the ocean to the temperature of 80° and 
upwards, considerable evaporation ensues, and each cubic 
foot of the air in the tropics may be said to contain, 
roughly, 8 grains of vapour at the temperature of 76° ; 
if that air be transported to these islands and reduced 
to their average temperature of 50°, it must part with 
nearly half its vapour, and would even then remain fully 
saturated. When one substitutes for grains and feet 
tons and miles, and reflects on the vast extent of the 
tropical oceans, there is no difficulty in understanding 
why winds from those regions deposit rain on all colder 
countries over which they blow. 

Why it falls has almost necessarily been ex- 
plained in the preceding section, but it may be well to 
point out that as the chief cause of rain is condensation 
by cold, and as hills are usually colder than the winds 
blowing against them, and likewise throw the air up 
to greater and colder altitudes, we naturally find the 
largest amount of rain in hilly districts exposed to 
currents of air coming direct from warmer oceans. 

How IT IS Measured. — This is so simple a matter 
that it hardly seems expedient to occupy much time 

Rain, Snow, Hail, &c. 139 

over it, but even with the simplest operation there is 
ahvays a wrong way of doing it, and as there is nothing 
worse than bad observations, I shall go rather fully into 
the subject. We want to know how much rain falls, 
that is to say, how deep the water would stand upon 
the ground after a fall of rain, if none of it penetrated 
the soil or flowed off it. Suppose the floor of this room 
to be level, covered with concrete, and provided with 
a ledge all round to prevent the water running off, surely 
that would give an accurate measurement of the rainfall. 
No, it would not, because it would be very difficult to 
measure accurately the depth of the water, and because 
evaporation from so large a surface would soon diminish 
the quantity to be measured. Some form of funnel is 
therefore always employed. 

Different Patterns of Rain Gauges. — I will 
not take you through the entire variety of patterns of 
gauge hitherto employed, probably nearly a hundred, 
but select two, each typical of many gauges now in use. 
First, on account of its extreme simplicity, I take the 
pattern of gauge used in very wet and mountainous 
districts. It is merely a double cylinder, the outer one 
for protection, the inner one to hold the rain ; the inner 
cylinder is exactly the same size as the mouth of the 
gauge, therefore, if an inch of rain falls, the water in 
the inner cylinder will be i inch deep. A float 
rests on the water, and whenever it is desired to know 
how much rain has fallen, a rod, divided in inches and 
quarters, is dropped down until it rests on the float ; 
the height which the rod is above the receiving surface 

1 40 Aleteorological Lectures. 

shows the depth of rain fallen, I need not say that 
this is a rough plan, but it is accurate ; the gauges 
generally agreeing with ordinary ones within 4 or 5 
per cent. Secondly, I take a 5 -inch Snowdon gauge, 
because it is the pattern of which the largest number 
are now at work. It will be seen that the water of any 
ordinary rainfall passes into the bottle, and all evapora- 
tion is prevented, as the only access to the external air 
is up the long pipe. If the rainfall exceeds the capa- 
city of the bottle, or if the freezing of the water breaks 
the bottle, the record is not vitiated, because the water 
is retained in the cylinder, and can still be measured. 
The measurement is effected by pouring the water into 
a graduated glass, and as its area is perhaps only a 
tenth that of the funnel, it is evident that i inch of 
rain would fill such a glass 10 inches deep. 

Best Size, Shape, etc — Experiments have shown 
that in ordinary circumstances it is not of any conse- 
quence what is the size of the receiving surface, nor 
does it make much difference whether the gauge be 
round or square, but circular gauges are certainly the 
better, because (i) it is easier to make a true circle 
than a true square ; and (2) the influence of the rim (or 
the ratio of circumference to area) is less with a circle 
than with any other form. 

Respecting the material for gauges, there is no 
doubt that copper is the best ; but I may here address 
one word to manufacturers : many copper gauges are 
spoiled by being finished with edges rounded over iron 
wire ; the iron rusts and the gauge becomes shabby ; 

Rain, Snow, Hail, &c. 141 

a fold of copper is sufficiently strong by itself, and the 
iron is merely a source of weakness. Tin coated with 
japan is cheaper than copper, and lasts about ten years, 
but copper lasts — well, longer than any observer. 

Mechanical Gauges. — By mechanical gauges I 
mean those wherein the water by its own weight sets 
trains of mechanism in motion, but as these are nearly 
all bad, and are rarely used, I will pass them without 
further comment. 

Storm Gauges. — It is in the highest degree impor- 
tant to know accurately the rate at which rain falls. But, 
for this purpose, the ordinary rain gauge is of little use ; 
for, irrespective of the personal discomfort of standing 
in the rain in order to measure it at short intervals of 
time, the record would be vitiated by frequent inter- 
ference with the rain gauge funnel. I have therefore 
designed two modes of avoiding the discomfort and the 
errors. The first plan was to place a small funnel on 
the top of a long and narrow glass tube, of such a size 
that I inch of rain would fill about 2 feet of tube; the tube 
was mounted on a black board, and a white float rising 
on the top of the water showed the fall of rain. An 
overflow pipe allowed the measurement to extend to 2 
inches. This gauge was cheap, handy, and answered 
the two requirements of being read from indoors and not 
vitiating the true reading of the ordinary gauge. But 
it was awkward to empty, liable to be burst in frosty 
weather, not adapted for night observations, and trouble- 
some to read accurately in excessively heavy rain. 

I have here a greatly improved instrument, very 

142 Meteorological Lccttuxs. 

simple, very accurate, and, as far as I know, faultless. 
The rain passes through the funnel down the pipe into 
a cylinder, wherein there is a float which rises as the 
water falls, and as it rises it turns the two hands ; the 
longer (like the minute-hand of a clock) completes one 
revolution for I inch of rain, the shorter (like the hour 
hand) shows the number of inches, in this specimen 5 
inches ; but the number is simply dependent on the 
length of the cylinder, and by merely lengthening it 
the record could be extended to 10 or 20 inches if 
required for use where the rainfall is excessive. 

Altitude. — I must here also say a few words respect- 
ing the effect of the height above the surface of the ground 
at which a rain gauge is placed. Upwards of a century 
back it was known that rain gauges on lofty buildings 
collected much less than others near the ground. It 
seemed so strange that the nearer one went to the 
clouds the less was collected, that experiments were 
made in many places ; the best known series was made 
in this immediate neighbourhood, in 1766, by Dr. 
Heberden, F.R.S., who had three similar gauges con- 
structed, and placed, one in a garden near Westminster 
Abbey, one on the roof of a neighbouring house, and 
one on the centre tower of the Abbey ; the result was, 
that in the garden near Westminster Abbey there fell 
2 2'6i inches; on the roof of the house, i8'i4 inches; 
on the square tower of the abbey, i2'io inches. 
Similar experiments, and modifications of them, have 
been tried in many places, and almost always with 
similar results. The precise cause of the decrease was 

Rain, Snow, Hail, &c. 143 

long vigorously disputed, and to this moment the com- 
plete explanation of the fact has not been given. I 
believe, however, that it is now acknowledged to be 
almost entirely due to wind, although I do not myself 
understand exactly in what way the wind produces this 
effect. Some years since, a series of gauges, of which 
the funnels were not horizontal but tilted at angles of 
22i°, 45°, 6yh°, and 90°, and kept face to the wind by 
vanes, was erected at the cost of Mr. Chrimes of 
Rotherham. On discussing the observations, I obtained 
results whence the preponderating influence of the wind's 
velocity seems indisputable. Recently, Mr. Dines has 
been making experiments of a similar character on the 
tower of his residence at Hersham, and these are shown, 
by the analysis given by Mr. Rogers Field in the Meteor- 
ological Magazine, to be in remarkable agreement with 
the wind's direction. 

I ought, perhaps, to add that, as this diminution is 
sensible even down to the surface of the ground, it is 
indispensable that observers report accurately the height 
of the mouths of their gauges above the ground, and, for 
the sake of uniformity, that all new gauges be at i foot 
above the grass. 

Necessity for Inspecting Rain Gauge Sta- 
tions. — Inspection always sounds like finding fault, and 
it must be admitted that such is its primary object, but, 
in my own case, I can truly say that it is much more 
agreeable when th^re is no fault to find. Measurement 
of rainfall is so easy and so simple, and the rules for 
observers are so ample, that there ought not to be 

1 44 Meteorological Lectures. 

much need for inspection. But there is ; and it is to 
be regretted that, owing to the absence of adequate 
pecuniary resources, this inspection is not more exten- 
sively carried out than it is. The only consolation is 
that, firstly, grossly erroneous rain-gauges, and good 
gauges badly placed, are now much more rare than 
formerly ; and secondly, stations are now so much 
more numerous that faulty records are less likely to 
escape detection. In the early days of inspection a few 
very gross cases were found, e.g. a rain gauge actually 
underneath a tree, another so close to a house that when 
the snow slipped off the thatch it fell on to the rain gauge, 
another with the edge of the gauge \ inch thick, instead 
of a knife edge ; a measuring jar graduated in cubic 
inches, and used as being hundredths of an inch of 
rainfall ; side tube gauges run empty at each obser- 
vation. But, on the whole, the observations, both 
old and recent, come out remarkably well ; a recent 
reduction of a group of about a dozen stations, in a 
tolerably level tract of country, showed only one dis- 
cordant record, all the others agreeing within an inch. 

Collection of Rainfall Statistics. — It seems 
to me that it must always be unpleasant to speak of 
work done by oneself If it has succeeded, the speaker 
appears to be praising himself, if it has failed, he can 
hardly like to say anything about it. Having had the 
guidance of the collection of the rainfall statistics of 
this country from the first large attempt, twenty years 
ago, up to the present time, I prefer, with your permission, 
to pass over that history, and deal merely with matters 

Rain, Snow, Hail, &c. 145 

as they stand now. First, as to the observers, they are 
mostly amateurs, of whom the total number is nearly 
2000, but besides them there are certain governmental, 
official, and semi-official stations, so that the total 
number of rain gauges, regularly observed in this country 
at the present time, is about 2200, say 1700 volunteer 
stations and 500 under one or other of the following 
bodies, viz. the Meteorological Council, the Meteorologi- 
cal Society, the Scottish Meteorological Society, the 
Board of Northern Lighthouses, Mr. Glaisher, and the 
Manchester, Sheffield, and Lincolnshire Railway. By 
a kindness which I fully appreciate, every one of these 
bodies sends me copies of its records, so that I am 
able to concentrate almost all (certainly 99 per cent 
of) the information obtained in the country. The 
advantage of such concentration is self-evident, and 
it is also partly reciprocal, for amid such a multitude of 
records it is far easier to detect errors than it would be 
to any one who receives only a few. The volunteer 
observers whom I have already mentioned, not only 
send up their returns regularly, but also contribute 
towards the unavoidably heavy expenses of checking, 
classifying, discussing, and publishing such a mass of 
statistics. Hence, and hence alone, it is that I am 
enabled to publish annually, at a comparatively low 
price, a general summary of all the rainfall observations 
made in the British Isles during the previous year. 
Nearly all the observations are made at 9 A.M. local 
time, and it often seems to me a remarkable illustra- 
tion of self-denial and willingness to help science, that 

146 Meteorological Lectures. 

as 9 A.M. sweeps across the British Isles from Lowestoft 
to the West of Ireland, no matter how wild the 
weather may be, forth go some 1500 or 2000 persons 
of all social ranks, from peer to peasant, to make their 
daily measurement of the amount of rain fallen. As to 
the position of these stations the best general idea is given 
by the map, but as it is a few years old, the present 
distribution is rather better than that shown by the map. 
With any large staff, changes by death and removal 
are unavoidable, and therefore constant vigilance is 
necessary to keep the whole country fully provided. 
At the present time observers are much needed between 
Thirsk and Whitby, and also in the S.S.W. of Ireland. 
Applications of Rainfall Data to Practical 
Life. — It is rather from plethora than from the reverse, 
that difficulty arises in this part of my Lecture. All 
the water in our rivers, lakes, and wells is stored rain ; 
and so is, therefore, every drop of water that we use. 
Rainfall details are often wanted for very strange pur- 
poses : I will quote one as a specimen. A chemist in- 
vented a method of preventing the streets requiring to 
be watered as often as is usual ; this he did by mixing 
with the water certain chemicals, which were calculated 
to abstract moisture from the air ; he contracted with a 
certain parish, and was to be paid so much per quarter, 
less the cost of any watering which the authorities 
might think needful. This arrangement of course im- 
plied that if his method succeeded, no deduction should 
be made. Vested interests in the water carts, however, 
were so strong that a tremendous deduction was claimed ; 

Rain, Snow, Hail, &c. 147 

the inventor obtained details of the times at which the 
carts were sent out to water the roads, and then rain- 
fall records showing that the watering carts were sent 
out while it was raining ! 

Drainage. — With the exception of one Irish en- 
gineer, I never heard any one maintain that drainage 
could be perfectly carried out without any knowledge 
of the fall of rain. The reverse is of course the truth, 
for in towns one must know what is the maximum 
storm rain to be dealt with, just as for bridges one 
must know the maximum flood which the bridge must 
be able to carry off. There are, however, wider, more 
scientific, and very valuable objects, which accurate 
rainfall data, supported by improved hydraulic arrange- 
ments, have effected in almost every country in Europe, 
except England, where we have such a reverence for 
vested interests that if a man has been injuring his 
neighbours for fifty years he has to be paid for ceasing 
to do so. It would probably be within the truth to 
say that the Hydrological commissions of Lyons and 
of the Seine have saved to France tens of thousands 
of pounds, and it would be equally true to say that the 
English Government has allowed the Thames to do 
damage to an equal amount. 

Flood Warning. — I have almost anticipated this 
subject in referring to Lyons and Paris, where there is 
a system of flood warnings in full operation. In both 
cases a system of rain-gauge stations has been organ- 
ised at the head of the watersheds ; daily reports are 
sent to the central ofiice, and so great is the experience 

148 Meteorological Lectures. 

gained by constant practice, that no flood ever reaches 
either city until long after its advent has been announced, 
and usually the height predicted is realised within a 
few inches. I do not for a moment say that Thames 
floods could either be prevented or precisely predicted, 
but as our great rain storms usually travel but slowly 
from west to east, and as the somewhat porous nature 
of most of England allows the rain to percolate, there 
is plenty of time to make arrangements which would 
mitigate evils which at present exist. 

Waterworks. — Excepting London (whereof the 
inhabitants seem too fond of Thames water to desire 
any with a purer history), it may probably be said with 
truth that half the urban population of the United 
Kingdom is supplied by gravitation waterworks, i.e. 
by the collection and storage of the rainfall on upland 
districts. This is another point of contact between 
rainfall researches and practical life, for accurate know- 
ledge of the amount of rainfall is indispensable for the 
proper designing of such works, and of determining the 
amount of compensation water to be sent down the 
streams for the use of the millowners upon them. 

Salmon Catching. — This is a subject which does 
not, at first sight, seem very intimately connected with 
rainfall, but investigations by Mr. Horsfall, carried back 
into the eighteenth century, appear to prove a distinct 
connection between the rainfall of one year and the 
weight of salmon sent to market in the following year. 

Sugar-Making. — One of the most elaborate in- 
vestigations of rainfall data ever undertaken was made 

Rain, Snow, Hail, &c. 149 

under the supervision of Sir Rawson Rawson while he 
was Governor of Barbadoes. A copy of his very 
valuable report is in the library of the Society, and 
therefore I need only say that Sir Rawson Rawson 
proves not only a distinct connection between the fall 
of rain and the total sugar produce of the island, but 
also that it is possible beforehand to predict within 
narrow limits what the total yield of the season will be. 
Effect of Altitude on Rainfall. — I now 
leave the applications of rainfall data, and come to some 
of the leading results hitherto obtained. It will perhaps 
be remembered that at the beginning of this Lecture I 
said that cold hill-tops acted as condensers. I am not 
sure that their action in producing rain is zvholly by 
virtue of their temperature, but, leaving debateable 
ground, we come to the undeniable fact that in ordinary 
circumstances there is a gradual increase in the fall of 
rain proportional to the altitude of the locality above 
the level of the sea. Roughly stated, the rainfall in- 
creases 3 or 4 per cent on its sea-level value for each 
100 feet of altitude above the sea. For instance, if the 
rainfall of the lowest part of London be 24 inches, then 
for the highest part of Hampstead (400 feet) we should 
have about 27 inches. This rule, though generally 
near the truth, is sometimes terribly wrong, especially 
in mountain districts. It is evident that it must be 
limited in its application by the fact that, as the rain 
comes from the clouds, as soon as the altitude becomes 
equal to that of the clouds the increase must cease, 
and so we find it, for the gauges on the top of Scaw- 

150 Meteorologica I L ecttt res. 

fell, Great End, Helvellyn, etc., collect less than those 
in the valleys near them, the gauges on these mountain- 
tops being often above the clouds. Irregularity is also 
produced by the different conditions which prevail on 
two sides of a hill, the rate of increase up the S.W. 
slope being different from that up the N.E., and both 
depending on the altitude of the summit ; accurate 
determinations of these rates are much required. 

Details of Mean Fall in British Isles and 
AT SOME Foreign Stations. — It would never do to 
crowd a lecture with a mass of figures, and yet figures 
are the end and aim of all rainfall work. I must 
therefore try to point out the broad features, keeping 
the details out of sight as much as possible. First, 
then, people have long spoken of mean rainfall, but the 
term was used for very inaccurate results. They took 
the arithmetical average of any number of yearly values 
they could get hold of, from 3 to 20, and without pay- 
ing the slighest attention to whether they were ordinary 
years, or very wet ones, or very dry ones ; they forth- 
with announced that arithmetical average as the mean 
rainfall of that place. The error of this mode of work- 
ing is greater the shorter the period (unless it be one 
specially selected), and vanishes if the period embraces 
20 years or upwards. In constructing a table of mean 
rainfall there are two evils between which it seems 
necessary to choose. The longer the period of observa- 
tion the more trustworthy is the mean deduced from it, 
but if one is only to work up long registers there will 
be large tracts of country without any. If one works 

Rain, Snow, Hail, &c. 1 5 1 

with short registers the means are hable to be in error 
through exceptional seasons not being adequately 
neutralised. I have adopted two ways of surmounting 
these difficulties. One is by taking first only the long 
registers, determining their true means, and the ratio 
which the fall in each year bears to the mean of the 
long period. Then, by applying these ratios to the 
observations which were made for only a few years, one 
obtains a very close approach to the true mean for 
those stations. Another plan is to take several long 
registers and to hunt through them for a short group of 
years of which the average is nearly the same as the 
average of a long period. The years 1860-65 form 
such a group, and the map is based upon a calculation 
of the mean fall during those six years at all the stations 
whence I could obtain records. It is tinted gradually 
deeper and deeper for each increase of 5 inches of mean 
annual rainfall. When it was prepared that map re- 
presented, as accurately as the time at my disposal 
allowed, the rainfall distribution over the country, but 
the number of stations has been so greatly increased of 
late years that I hope shortly to produce a far more 
accurate one. The general features will doubtless 
remain much the same, the alterations being, I expect, 
chiefly due to the insertion of local details. The map 
is so self explanatory that I need not say much about 
it. The tints are deepest where the total fall is great- 
est, but no attempt is made separately to denote ex- 
tremely wet stations, all those at which upwards of 75 
inches per annum fall being grouped together. The 

152 Meteoi'olog ical Lectures. 

localities at which this amount is exceeded are both 
few and small ; the largest is on the west of Scotland, 
but the one where the amounts are greatest is the 
English Lake District, where several stations have an 
annual rainfall of 100 inches ; one, Seathwaite in 
Borrowdale, at the south end of Derwentwater, has an 
average of 140 inches; and a little above it, on the 
slope of the hill, near Stye Head, the mean fall is 175 
inches, or about i 5 feet, and in wet years it is consider- 
ably more than 200 inches or 17 feet. 

Foreign Raix. — It would take an entire evening 
to treat properly of the rainfall of the globe, and there 
is also another reason why I should not attempt it, 
namely, that for large tracts of land we have no records, 
and for other parts their accuracy is doubtful. I 
must not dwell longer upon it than to say that while 
there are parts of the earth's surface where the fall of 
rain is so rare that they are called rainless^ there are 
others where the fall is twenty-four times as great as in 
London. Both extremes are to be met with in India, 
or upon its borders, for instance at Kurrachee, in the 
N.W. of India, where the mean annual fall is only 7 
inches, and it is less still further to the N.W. ; on the 
contrary, on the Khasia Hills, N.E. of Calcutta, the 
average is generally said to be 610 inches (or 5 i feet), 
but I have not seen any recent returns from that 

I must not, however, leave you with the impression 
that no progress is being made towards an accurate 
survey of the rainfall of the world, but the work is so 

Rain, Snow, Hail, &c. 153 

gigantic that at present we have only fragmentary- 
monographs, I may mention briefly some of the best ; 
for Europe the Regenkarte, by Dr. Otto Kriimmel ; for 
India the map compiled I believe originally for Dr. 
Brandis, and reprinted annually in the blue book East 
India {Progress and Condition) ; for the United States 
in the Smithsonian tables by Schott ; and for Africa in 
the very original and interesting article by Keith 
Johnston in Stanford's recent book upon that country. 
Copies of all these maps are on the table. Thanks 
largely to the energy of Mr, Todd of Adelaide, we 
shall soon be able to know much of the rainfall even 
of central Australia. 

Seasonal Distribution. — This feature of rain- 
fall distribution is very marked in some tropical regions, 
as, for instance, at Bombay, where G'j inches fall in the 
four months June to September, 2 inches in October, 
making 69 inches in five months, and only i^ inch in 
the 7 months between October one year and June of 
the next. At other stations rain occurs almost daily 
throughout the year. In the United Kingdom the fall 
is nearly equally distributed throughout the year. At 
dry stations October is usually the wettest month, 
except at stations where heavy thunder-storm rains 
have occurred repeatedly in July or August ; April is 
generally the driest month. At wet stations the 
proximity of mountains has a curiously marked effect 
upon the curve of monthly rainfall, as it so largely 
increases the fall in the winter months as to make 
December or January the wettest month of the year. 

154 Meteorological Lectures. 

This is a feature not yet generally recognised by 
hydraulic engineers, but of great importance, for summer 
rains are so reduced by evaporation that it is the winter 
rains which are of the greatest utility, and their dispro- 
portionate excess in mountain districts adds enormously 
to the yield of those districts. 

Daily Fall and Storm Rains. — It will not be 
possible to separate these two items of the syllabus, and 
therefore I mention them together. Daily falls of small 
amount do not call for special notice ; daily falls of large 
amount are generally due to storms. In the British 
Isles the greatest amount on one day in each year, at 
all the stations, is about \\ inch, but no year passes 
without far heavier falls at individual stations, at one or 
more of which upwards of 4 inches always fall (hence 
follows the rule, that all rain gauges must hold at least 
that amount). The extreme amount which can be de- 
posited in twenty-four hours in the British Isles is not 
known ; it is a question of catching and measuring a 
broken waterspout. Measurement of the water flowing 
off Black Hambledon, near Todmorden, on July 9, i 870, 
indicated, according to the local surveyor, Mr. Green- 
wood, a rainfall of at least 9 inches, and when the dis- 
astrous rain of August 6, 1857, occurred at Scarborough, 
the only rain gauge in the town, one which held g\ 
inches, was found to be full and overflowing. 

These British amounts sink into insignificance be- 
side those produced by the monsoon rains in India ; 
such as, for example, 15*31 inches on June 27, 1869, at 
Bombay, and 25-49 on July i, 185 i, at Cherrapoonjee. 

Raiii, Snow, Hail, &c. 155 

Secular Variation. — I do not like this term. I 
need not say that it has no reference to things temporal 
as distinguished from others, neither does it refer, as 
some dictionaries make it, merely to events occurring 
once in a century. One cannot say periodicity, because 
that implies the recurrence of identical phenomena at 
periodic times, whereas all that I desire to convey is 
the idea of changes which are traced through long 
periods of years. 

In "Ct^Q Report of the British A ssociationiox 1866 I gave 
the full details of calculations whereby I obtained the 
approximate rainfall of each year from 1726 to 1865, 
and though it gave no clue to the law of sequence of wet 
and dry years, it did bring out one rather alarming fact. 
For waterworks' purposes engineers often calculate upon 
the yield of three consecutive dry years, and consider 
that the average of three such years will be ^th less 
than the mean of a long period, i.e. that it will be 
about 83 per cent of the truth. In the middle of the 
eighteenth century there was a period of thirteen con- 
secutive years, from 1738 to 1750 both inclusive, with 
an average rainfall of only 71 per cent; even if we 
assume these observations to be 10 per cent in error, 
we still have thirteen consecutive years with only yZ 
per cent, instead of three years with 83 percent. Such 
a drought as that would, under the altered circumstances 
of the present day, produce inconvenience and suffering 
of a very important character. I see no reason why it 
should not recur, and I certainly know of no one who 
has taken the possibility into consideration. 

156 Meteorological Lectures. 


What it is. — Snow is ice. Yes, the gentle snow- 
flake which will fall and rest upon a spider's web without 
breaking it is the same material as will support the 
weight of thousands of persons, and vehicles of almost 
any weight. It is not easy to the untrained mind to 
realise that snow is a hard substance, its remarkable 
lightness, whiteness, and softness being wholly due to its 
extremely delicate structure. Snow is frozen vapour, and 
if in its fall it neither passes through strata of air above 
the temperature of melting ice, nor meets that tem- 
perature upon the earth's surface, it falls in figures of 
such extreme beauty that no words of mine could ade- 
quately describe their elegance. I therefore take a 
few from the masterly pen of John Tyndall. 

Professor Tyndall describes a fall of snow he wit- 
nessed on the summit of Monte Rosa, as " a shower of 
frozen flowers ; all of them were six-leaved ;■ some of 
the leaves threw out lateral ribs like ferns ; some were 
rounded, others arrowy and serrated ; some were close, 
others reticulated, but there was no deviation from the 
six-leaved type. Nature seemed determined to make 
us some compensation for the loss of all prospect, and 
thus showered down upon us those lovely blossoms of 
the frost, and had a spirit of the mountain inquired my 
choice — the view, or the frozen flowers — I should have 
hesitated before giving up that exquisite vegetation. 
It was wonderful to think of, as well as beautiful to 
behold. Let us imagine the eye gifted with a micro- 

Rain, Snow, Hail, &c. 157 

scopic power sufficient to enable it to see the molecules 
which composed those starry crystals ; to observe the 
solid nucleus formed and floating in the air ; to see it 
drawing towards it its allied atoms, and these arranging 
themselves as if they moved to music, and ended by 
rendering that music concrete. Surely such an exhibi- 
tion of power, such an apparent demonstration of a 
resident intelligence in what we are accustomed to call 
' brute matter,' would appear perfectly miraculous, and 
yet the reality would, if we could see it, transcend the 
fancy. If the Houses of Parliament were built up by 
the forces resident in their own bricks and lithologic 
blocks, and without the aid of hodman or mason, there 
would be nothing intrinsically more wonderful in the 
process than in the molecular architecture which de- 
lighted us upon the summit of Monte Rosa." 

Even in the temperate climate of London in about 
one snowfall out of five it will be found that the snow, 
instead of being, as most people regard it, a mere 
irregularly agglomerated mass of light ice, is really 
crystallised in exquisitely beautiful forms. The crystals 
are rarely less than j^th of an inch across, and therefore 
their general form is easily visible without a lens. Six- 
rayed snow is said by Kepler to have been mentioned 
by Socrates, but I have not been able to find the 
quotation. The earliest reference to these figures which 
I have yet found is in the work by Olaus Magnus, 
Historia de Gentibus Septeiitrionalibus, published at 
Rome in 1555, wherein the author says : " In one day 
and night you shall see fifteen or twenty distinct forms 

1 5 8 Meteorological L ec lures. 

of snow," but he gives no engravings. The earliest 
that I have seen are in a very rare tract, written in 
1 660 by Thomas BarthoHnus, De Figurd Nivis. I must 
not allow myself to drift into the bibliography of snow 
crystals, but may just mention that among those who 
have written upon the subject are, besides those already 
mentioned, such great names as those of Descartes and 
Cassini. The finest early collection of engravings 
(upwards of 400) are in a work, De Sneeuw Figuurcn, 
published at Haerlem, in 1747, by Dr. Engelman. 
Lastly, we come to by far the largest and finest set, 
finest both artistically and scientifically, because they 
are the most beautiful and the most accurate. I mean 
those observed by Mr. Glaisher, and engraved in the 
fifth Annual Report of this Society. I cannot pretend 
to represent them in all their graceful beauty, and have 
not selected the prettiest, but those which are so common 
that they are to be found in nearly all the sets of 
engravings ; though the finer details are only given in 
Mr, Glaisher's paper. 

One word as to the best mode of observing these 
crystals. The first caution to be given is, do not breathe 
towards them ; all the finer details would be instantly 
melted, and you would either see heavy patterns, or, 
more probably, none at all. Roughh', and without 
apparatus of any kind, many beautiful crystals may be 
seen lying on previously fallen snow ; it affords a bed 
both cold and soft, and they will lie on it unchanged 
for hours. For accurate work, slips of coloured glass, 
set at various angles, and allowed to become quite cold, 

Rain, Snow, Hail, &c. 159 

afford excellent receiving surfaces, and a strong lens or 
very low-power microscope can then be used. Pro- 
vided the figure be symmetrical, it is only necessary to 
draw the details on one radius, the other five can be 
added subsequently. 

Measuring Snow. — Snow sometimes puzzles rain 
observers, as it is not so easily measured as rain. Very 
simple rules have been drawn up, and therefore I will 
not enter upon the subject. Very roughly, i foot of 
snow may be taken as equal to i inch of rain. 


What it is. — When one can find in existence a 
paragraph which exactly suits one's purpose, I think it is 
better to quote it and acknowledge the origin, than to 
twist it round and pass it off as original. I do not know 
how to commence this section better than with a para- 
graph from Mr. Glaisher's translation of Flammarion's 
L'A tnwspJicre. " Hail occurs during a thunderstorm when 
the temperature is very high upon the surface of the 
ground, but decreases rapidly with elevation. This rapid 
decrease is the principal element in the formation of hail, 
and it has been known to be as much as 1° in a little 
more than 100 feet. What then takes place in the 
region of the clouds ? Those above, from 10 to 20 or 
25 thousand feet high, contain, the highest of them, ice 
at about -30° Fahrenheit, the lowest of them vesicular 
water at about zero Fahrenheit. The lower clouds con- 
tain vesicular water above 32°. As a rule, these clouds 
travel in different directions, and hail is formed when 

1 60 Meteorological Lectures. 

there is a collision and admixture of winds, currents, 
and clouds, the temperatures of which are different. The 
vapour which then resolves itself into rain freezes instan- 
taneously in so low a temperature." It will be observed 
that in this paragraph no part in the formation is 
ascribed to electricity. It is obvious that such mixtures 
of air-currents as those above mentioned must produce 
great electrical disturbances, and many theories invoking 
electricity as the cause of the formation of hail, have 
been put forward. It is proverbially difficult to separate 
cause and effect, but as the causes above stated seem 
to be sufficient, I prefer to leave the electrical pheno- 
mena in the class of effects. 

Some of its Forms. — Hailstones in this country 
are usually the size of peas, and approximately spheri- 
cal, but these are the ordinary and unimportant stones. 
Scarcely a year passes without the fall of very different 
stones. A black cloud is seen in the south, a roaring 
sound (like a wave retreating over a pebble beach) is 
heard, and in five minutes the standing crops are 
thrashed, thousands of panes of glass are broken, the 
ground is covered with from 2 to 6 inches of ice, 
and a blaze of sunshine illuminates a scene of desolation. 
The hailstones in this country are not often more than 
2 inches across, but even these hit very hard. I 
remember seeing in the suburbs of London a pony, 
which two days previously had been exposed to a hail- 
storm, and whose back was covered with lumps arising 
from the blows he had received. In the hail-storm 
which passed over Stronsay in the Orkneys in 1 8 1 8, it 


Rain, Snow, Hail, &c. i6i 

is stated that " not only were nearly all the geese and 
smaller fowl killed, but the terrified black cattle and 
horses, which had broken their tethers, and been ob- 
served at the beginning of the fall of hail running 
violently backward and forward, galloping and flinging, 
had now collected together in a herd. Mr. Caithness 
at length made his way to them through the half- 
melted ice ; they still trembled exceedingly ; some of 
the horses had lain flat down on the grass, with their 
heads stretched out, and all of the animals were more 
or less cut and bleeding. Some of the weaker horses, 
the farmer says, will never recover ; the milch cows, he 
adds, were ' struck yeld,' or gave no more milk, and, in- 
deed, Avould not suffer the people to attempt to milk 
them any more." 

I am afraid to say anything respecting extremely 
large hailstones, for you will scarcely believe me. I did 
hope to put before you to-night a piece of corrugated iron 
roofing, perforated by a recent hail-storm in India, but 
I have mislaid the address of the gentleman who has 
brought it over, and therefore that very indisputable 
evidence is not forthcoming. 

The shape and density of hailstones vary greatly ; 
they usually show more or less of a radial structure, 
and are often formed of concentric shells of alternately 
clear and opaque ice. A very fine collection of engrav- 
ings is given in Abich's paper, Uber Krystallinischen 
Hagel im Tlirialethischen Gebirge, published at Tiflis in 
the Caucasus. 

Noise before it falls. — This I have already 

1 6 2 Meteorological L ectures. 

mentioned ; it is doubtless due chiefly to the stones 
striking each other, and partly to their striking build- 
ings etc., in their line of approach. 

Rarity at Night. — This is well known, but I 
have never seen it explained, although it seems to me 
that if hail at night were not a rarity, it would be im- 
possible to accept the explanation of its formation 
which I have already given. Hail is rare at night 
because the air is not then usually " very hot near the 
surface of the ground," nor does the temperature then 
" decrease rapidly with elevation." The conditions 
requisite for the formation of hail rarely exist, and 
hail is equally rare. 

Atmospheric Electricity. 

Both from want of time and from want of ability, 
I am unable to treat this subject properly. Had other 
circumstances permitted, an evening would have been 
devoted to it, and then, it is needless to add, the Lecture 
would have been given by some Fellow less incompetent 
than myself. But rain, hail, and thunderstorms go to- 
gether, and therefore, nolens volens, it appears in my 
syllabus. It used to be the fashion to ascribe to the 
action of electricity all unexplained phenomena ; a wiser 
course is now adopted, and people are not too conceited 
to own that they do not know everything. 

I shall not attempt to give a connected statement 
respecting atmospheric electricity, but merely some 
scraps of information which may perhaps induce others 
to devote themselves to the subject. 

Rain, Snow, Hail, &c. 163 

Years ago, when Francis Ronalds was director of 
Kew Observatory, the upper portion of that building 
was fitted up with such a collection of electrometers 
as had never been established before, and has never 
been equalled since. Respecting the results obtained, 
I would refer you to the Reports of the Kew Committee, 
to Kaemtz, and to Drew. 

At the Royal Observatory, Greenwich, attempts 
have been made for many years to observe atmospheric 
electricity, but they have been very unsuccessful, the 
insulation of the exploring wire having rarely been 
perfect for long together. 

The most elaborate experiments with exploring 
wires were those made on the Ouantock Hills, in Somer- 
setshire, by Andrew Crosse. Much intensely interest- 
ing information is given in the "Memorials" published by 
his widow. I may mention one statement, viz. that 
frequently storm clouds appeared zonal, that is, alternate 
portions positively and negatively electrified. 

For general and very rough purposes an ordinary 
gold-leaf electrometer gives useful indications, but it is 
far inferior to even the cheapest form of Sir William 
Thomson's electrometer, which is certainly the instru- 
ment of the present, and possibly of the future also. 

People often speak of summer sheet lightning as 
harmless — so it is to them. I early learned that it was 
by no means always as harmless as it looks, and my 
experience may fix the fact in your memory. Many 
years ago, one lovely summer evening,! saw from London 
beautiful lightning playing along the S.W. and W. 

1 64 Meteorological Lechires. 

horizon : I watched it for an hour, and enjoyed the sight. 
Two days afterwards tidings arrived of a fearful thunder 
and hail storm at a village some 30 miles from 
London, and that in a row of cottages belonging to me 
not one pane of glass on the south side was left whole. 
Lightning is visible at great distances, I believe as 
far as 150 miles; thunder is stated to be audible for 
only about 10 miles, but Mr. Corder in the October 
number of the Natural History Journal z^y?,, under date 
September 8th, " Counting the seconds between the 
flash and the thunder I got twice up to 130 seconds, 
or 27 miles distant. This is the farthest I ever counted. 
Flammarion gives 10 miles as the maximum distance at 
which thunder is audible ; but I have heard it several 
times at about 100 seconds, or 21 miles." 

The frequency of English thunderstorms increases 
with the temperature, but it is also greater with hot 
damp weather than with hot dry weather. 

Summer thunderstorms are supposed to be more 
destructive than those of other periods, but the larger 
percentage of accidents may be due to more people 
being in the fields, and stupidly sheltering under trees, 
in summer. 

Lightning Conductors.— I cannot understand 
why English people have hitherto been so slow to erect 
lightning conductors, nor why, when they do put them 
up, they are made so stunted that they look as if ashamed 
to show themselves. A properly fitted and cared-for 
conductor gives absolute protection to the building on 
which it is erected, and if, as the saying is, " A penny- 

Rain, Snozu, Hail, &c. 165 

worth of ease is worth a penny," it is strange indeed 
why some people allow their nervous system to be 
deranged instead of so protecting their houses that they 
may be able to watch with calmness and with pleasure 
one of nature's grandest sights. 

Although the general principles which govern the 
erection of lightning conductors are well known, there 
are some minor points which require discussion. I am 
glad to end these disconnected remarks by informing you 
that delegates from the Physical Society, the Society 
of Telegraph Engineers, and the Royal Institute of 
British Architects, have accepted an invitation from the 
Council of this Society, and are endeavouring to settle 
all doubtful points. I must not mention names, but the 
delegates are nearly all men of cosmopolitan renown. 

One remark in conclusion. — The leading idea which 
it was my wish to urge upon you seems constantly to 
have escaped mention. Perhaps, however, it is well that 
it has been so, for last words are sometimes longest 
remembered. I desire to impress upon you my firm 
conviction that the great need of rainfall work, as of 
every other branch of meteorology, is neither more 
observations nor more money (though neither of these is 
to be despised), but more brains, more hard workers, 
more deep thinkers. 



Meteorology is the science of the atmosphere, of 
TO, fierecopa, the things above the earth, as Aristotle has 
it, and its interest to every one hardly needs remark. 
Inasmuch as in the air " we live and move and have our 
being," any knowledge which we can gain from time to 
time of its condition, and of the changes which are 
taking place in it, cannot fail to be of importance to our 
material welfare, our health, and our comfort. 

Almost every one imagines himself a born meteoro- 
logist, at least in so far as every one is perfectly ready 
to volunteer an opinion on the prospects of the day's 
weather, and from the earliest ages men have been 
watching the sky and the changes in its covering, and 
recording their experiences. Who that has read Greek 
does not know the humour with which the meteorological 
theories of the Athenian weather-prophets are ridiculed 
by Aristophanes in T/ie Clouds? Nevertheless, though 
men have studied meteorology more or less system- 
atically since the time of Aristotle, who wrote the first 
treatise on the subject, but little progress was made in 
the science until the invention of the barometer and 

The Nature, Methods, &c., of Meteorology. 167 

thermometer some 200 years ago. And we must admit 
that even yet it has hardly made good its title to a 
place among the exact sciences. 

The reason of this is easily explained — Firstly, we 
live at the bottom of the atmospheric ocean, and of this 
the upper layers are all but utterly inaccessible to us, so 
that what half-knowledge we can gain of their condition is 
mostly derived from conjecture. We know really nothing 
of any phenomenon occurring above the level of the 
stratum which we inhabit. Secondly, the observations we 
make of the physical state of the air are affected to such a 
degree by local accidents, such as the elevation, contour, 
and slope of the ground, nay, even by the very character 
of the soil, that we meet with material variations of 
meteorological circumstances even within the limits of 
a single county. In this respect meteorology offers a 
strong contrast to astronomy, the recognised queen of 
all the exact sciences. The objects of observation and 
study which are pursued by astronomers are at such a 
distance from our planet, that it is practically of little 
importance whether the observer be placed at Green- 
wich, at Rome, or at Washington. The phenomena 
themselves are identical, and other things being equal, 
the difficulties of effecting the observation depend 
mainly on the meteorological conditions of the locality. 
In fact, in the absence of clouds, the range of phenomena 
within the ken of an astronomer is limited only by the 
horizon of his station and the power of his telescope. 

But in meteorology the case is widely different. 
The phenomena are not the same at two different points 

1 68 Meteorological Lcchtres. 

of observation. The temperature of the air and the 
motion of the wind in the street outside differ appreciably 
from what is being experienced in the middle of Hyde 
Park, and a fortiori from what is felt outside the city, as 
at Kew or Greenwich. 

Hence we see the necessity of covering the country 
with, a network of independent meteorological stations 
for climatological purposes, as the observer at each 
place cannot do more than record the phenomena ex- 
hibited by the actual particles of the atmosphere which 
come in contact with his instruments. In fact, we may 
exemplify the difference between the two sciences by 
an illustration taken from biology. The astronomer 
may be compared to one of the more highly organised 
among the mollusca, such as the octopus or the argo- 
naut, which is endowed with powers of motion, and can 
seek its food afield, while the meteorologist is, like a 
mussel or an oyster, anchored to one spot, and obliged 
to make the best of such nutriment as may chance to 
be swept within his reach. 

If we seek to investigate the climate of a thinly 
peopled region, like one of our Australian colonies, we 
are thankful if we secure stations even 250 miles apart, 
but when we come to the consideration of our own 
climate at home, we find that a distance of 50 miles 
is still too great to ensure that no special peculiarities 
shall escape our notice, and expose us to the charge of 
unduly depreciating, or of not being keenly alive to, the 
climatic advantages of each rising watering-place. 

In all this multiplication of stations we must not 

The Nature, Methods, &c., of Meteorology. 169 

hold that quantity will in any way replace quality. The 
results from one bad station in a district will often 
throw doubt on the figures of most conscientious 

In more than one instance of recent times, it has 
come out that results obtained by laborious calculation 
have been proved to be almost worthless, owing to the 
disregard in former times of obvious precautions to en- 
sure accuracy in the observations and their registration. 

This is sufficient to show that it is not enough to 
buy good instruments, and set them up with due re- 
gard to exposure, etc., unless you can provide an accurate 
and punctual observer, and ensure that, when this per- 
son chances to be absent, a thoroughly competent 
substitute shall be ready to take his or her place. I 
say Jier advisedly, for ladies, thanks to their patience, 
are some of the best observers we can have. 

The duty of observing regularly is not an easy task. 
In this busy country observers would object to observe 
three times a day, and yet that is a sine qua non in 
most other systems. We here only ask for readings at 
9 A.M. and 9 P.M., and yet our observers find the latter 
hour very irksome. 

Meteorology, like all other sciences, demands self- 
denial from her votaries, and there are but few men who 
would be willing, if their life was spared so long, to 
record steadily in one district for more than half a 
century, like my friend Dr. Charles Clouston, of Sand- 
wick Manse in the Orkneys. 

There are but few recognised observatories of which 

I JO Meteorological Lectures. 

the registers, of uniformly high character, go back for 
fifty years. The accurate records at each spot simply 
correspond with the period of office at the place of 
individual observers. When each died or left the place, 
the chain was broken. 

In recent inquiries into rainfall periodicity, the 
tables cited have been from widely different localities, 
and when my friend Mr. Dines published, some years 
ago, his tables of the rainfall of London, he could not 
find, even for our National Observatory at Greenwich, 
a record of so simple a nature as that of rain kept with 
its present accuracy, before I 815. 

If, then, we find difficulty in securing accurate in- 
formation for the climate of our highly civilised Europe, 
what are we to say about our knowledge of the climates 
of the other continents. This is scanty enough, if we 
look for data of high scientific value. On a recent 
occasion our secretary, Mr. Symons, published a valu- 
able summary of the existing statistics of the climates of 
our colonies, but full as were the details in that paper, 
it showed us how much we have still to learn, before 
we can pretend to have gained a really comprehensive 
insight into the meteorological conditions of the globe. 

The earliest systematic effort to obtain this informa- 
tion was the scheme organised in this country by the 
Committee of Physics and Meteorology of the Royal 
Society in 1840, and managed by Sir E. Sabine. A 
similar system was conducted in Russia under Kupfifer. 
The original raison d'etre of this system was the con- 
firmation of the Gaussian theory of Terrestrial Magnet- 

The Nature, Methods, &c., of Meteorology. 171 

ism, but Meteorology was also embraced within its 
scope. The results obtained at these colonial observa- 
tories have, in the few instances in which they have 
been discussed, thrown a flood of light on the condition 
of the atmosphere in widely different parts of the globe. 
It is a great pity that this system has not been con- 
tinued. Of the four of our colonial observatories only 
two. Cape Town and Toronto, survive. The Russians, 
however, have at all events maintained their stations, 
which continue to furnish valuable information from 
the distant regions of Siberia. 

We are therefore compelled to admit that any 
accurate knowledge we possess of the meteorology of 
the globe is in great measure derived from observations 
taken over a comparatively limited portion of the 
northern hemisphere. In all this talk about the 
demand for new stations, I must not be supposed to 
deny that, on numerous questions of great importance, 
abundance of material exists for any one who wishes 
to discuss it. The most pressing want of meteorology 
at present is, as Mr. Symons justly says, not observa- 
tions, but brains to utilise them. 

The stations which I have hitherto mentioned have 
been all on land, but as the sea takes up two-thirds of 
the earth's surface, we must not disregard it as an 
area for the collection of information. This is easy 
enough to say, but when we reflect a moment, we see 
that the problem is one of extreme complexity. To 
illustrate my meaning by a familiar illustration, I would 
say that the endeavour to give a correct account of 

172 Meteorological Lechires. 

the climate, etc., of any district of the sea, presents 
much the same prospects of success as we should have, 
were we set to determine the climate of the different 
parts of France, from observations made by English 
tourists in their railway journeys through the length 
and breadth of the land. Ships at sea can never rest 
unless becalmed or hove-to, and so the observations 
made at noon to-day may be taken at a spot 300 miles 
distant from the ship's position yesterday or to-morrow. 
Hence we see the comparative fruitlessness of the 
attempts to deduce means of any value from the log 
of a single ship, no two successive observations having 
been made under exactly the same circumstances, 
except when she was at anchor. 

What we have to do is to take a definite area, 
say a one-degree square, in any part of the sea, and 
deal with all the ships which pass through it. Sup- 
posing that these ships have similar instruments and 
equally qualified observers, we are met at once by this 
difficulty : — Suppose that this square really had seven 
days of easterly wind in each of two months, and that 
only one ship passed through it in each of the months. 
A, bound to the eastward, would probably record twenty 
observations of the east wind, as she would be beating 
against it and detained in the square, while B, bound 
westwards, would fly through the square, and probably 
only put down the east wind twice. What is the true 
record of the wind for either month ">. 

C again may have been becalmed in the square for 
three days in an anticyclone, with his barometer rang- 

The NaUirc, Methods, &c., of Meteorology. 173 

ing above 30*5 inches, while D, on another occasion 
may have been hove-to in a winter gale, with his baro- 
meter below 29 inches. 

In every one of these cases the local conditions 
will affect the observations taken, and any means ob- 
tained from their discussion. How are we possibly to 
lay hold of the sound web of truth which lies under 
this motley tangle of conflicting information } The 
problem is a tough one to solve, but we think that we 
have partially solved it for some small areas. 

The complication is even worse than I have de- 
scribed when we wish to deal with the climate of the 
sea at large, for we find that information cannot be 
got from certain unfrequented parts of the sea, unless 
ships are sent on purpose to get it, and this is a result 
not easy of attainment. 

We see that in dealing with ocean meteorology it 
is nearly hopeless to look for a complete representation 
of the geographical distribution of meteorological con- 
ditions, and that no matter how carefully we collect 
and discuss our information, a large part of the isobars 
and isotherms which have been drawn over the sea are 
mere approximations. Still, when we look at the great 
amount of meteorological knowledge which has been 
deduced from the logs of our marine observers, we take 
courage and feel that although it may be long before 
absolute truth is obtained, we are yet bringing out valu- 
able approximations for the use of the navigator, as 
well as for the physical geographer. 

I have hitherto dealt with the subject of observing 

1 74 Meteo7'ological Lectures. 

stations solely in relation to climatology and the physics 
of the atmosphere. There is, however, another direc- 
tion in which it may be prosecuted, and of which the 
importance cannot be over-estimated — that is the study 
of weather. We may almost say that this is a new 
science, rendered possible by the facilities of com- 
munication afforded by the electric telegraph. 

This branch of inquiry demands heavy expenditure, 
and a great amount of discipline and organisation, so 
that it cannot be prosecuted by individual observers, 
or at isolated stations, no matter how perfectly they 
may be equipped and managed. In his latest report 
General Myer congratulates his Government on possess- 
ing in the observingstaffof the Chief Signal Office, a body 
of drilled men available for the suppression of any riot 
or disturbance. The idea of our thirty telegraphic 
reporters forming a volunteer corps is rather amusing. 

This line of inquiry — weather telegraphy — in no way 
falls within the scope of objects followed by our Society. 
I need not therefore detain you by describing its 
methods ; I would, however, point out one broad feature 
of distinction between climatology and weather study 
as regards the collection of observations. In the former 
case, as you have just heard, we seek above all for con- 
tinuous records from the same spot. In the latter, 
geographical position and freedom from conditions 
which will affect the character of the observations, 
especially of wind, are of paramount importance. If 
an opportunity occurs of obtaining a report from a new 
station which will give us earlier and surer intimation 

The Nature, Methods, &c., of Meteorology. 175 

of coming changes of weather, we reject ruthlessly 
offers of observations from the most ably served ob- 
servatory in the district. 

As regards synoptic work on a large scale, the 
importance of which to the meteorology of the future 
is being daily more and more acknowledged, it is evi- 
dent that the records of the oldest established station 
are of no higher value than those of a ship on her rapid 
passage over the ocean. 

Here we come to a point of view from which we 
may look our critics in the face and boldly ask for 
more, no matter how our shelves may be bending be- 
neath the weight of undiscussed records. When we do 
ask for more, however, it is not from these islands or 
from the more civilised countries, but from the " unsur- 
veyed world " of Africa, Central Asia, Australia, South 
America, and our own north-west American territories. 
I need hardly say that meteorological processes go on 
whether men be present to register them or not, and, 
could we get it, a knowledge of what is going on at 
present over at least the whole northern hemisphere 
would be necessary for the complete elucidation of the 
agencies which produce our weather. 

We do not want more synoptic stations in these 
islands, for we have far too many already. Upwards of 
sixty observers have sent in their names to join in the 
Washington Scheme, and there is not room for six 
wind arrows for the British kingdom on any charts 
which are likely to be published to show the sequences 
of weather in the northern hemisphere. At the present 

1 76 Meteorological Lectures. 

moment one good station on Spitzbergen or Jan Mayen 
would be worth as much as ten in Western Europe. 

Here I may be allowed a short digression to say 
that, in the cause of science, it must be a matter of 
regret that the far-seeing scheme, which has lately been 
revived by Count Wilczek and Lieutenant Weyprecht, 
of girdling the North Pole with a belt of observing 
stations, does not exhibit many symptoms of vitality. 
The plan is not sensational enough to attract extensive 
public notice, and there is too much ground for fear 
that it will never come to a worthy realisation. 

I have hitherto been speaking mainly of the collec- 
tion of meteorological observations, and must now 
briefly touch upon the methods of the science. I must 
reluctantly admit that these are not by any means 
satisfactorily settled as yet. While some meteorologists 
complain of an unnecessary and inquisitive interference 
with the time-honoured habits of practised observers, 
and decry all attempts of International Congresses to 
introduce uniformity of procedure and publication, 
others come forward to demand the excommunication 
of every observer who does not conform to recognised 
rules, by ivhich they vican the regulations enforced in their 
own special organisation. The cry of these gentlemen 
is for uniformity in instruments, methods, and hours, 
and they tacitly assume that no one has a right to a 
voice in the matter who does not accept their dicta. 
The fact is, that on all the points which I have noticed, 
great differences of opinion and practice exist. As to 
instruments, the Russians call for siphon tubes, while 

The Nature, Methods, &c., of Meteoi^ology. 177 

we prefer Fortin's or Kevv pattern barometers. For 
thermometric exposure the battle of the screens is raging 
with its full fury. The Italians hold to their north-side 
exposure, the " Fenestra Meteorologica." The Nor- 
wegians, in great measure the Germans, and the Dutch, 
do the same. The Russians, and we ourselves, have free- 
standing screens designed to cut off all radiation ; and 
lastly the French, at least at several stations, place the 
thermometers among trees or shrubs, with a simple board 
to keep off the direct rays of the sun. 

How can we look for minute accuracy in results 
with such wide differences of procedure } the idea is 
simply absurd ! 

In hygrometry too, what tale does Mr. Dines tell, 
in the latest part of our Journal, of the differences in 
the determination of the dew point by his own ap- 
paratus and by the ordinary methods 1 Again, who 
will maintain that the wet-bulb gives any satisfactory 
indications in time of frost .'' Are we on this account 
to go back to the half-forgotten hair hygrometer of 
Saussure .'' 

These statements are sufficient to show that, as 
regards methods, we are still in want of suggestions 
from experienced physicists ; as regards hours of ob- 
servation, what are we to say } At the first meteoro- 
logical conference, thirty-three years ago, at the Cam- 
bridge Meeting of the British Association in 1845, the 
meteorologists present agreed to differ on this knotty 
point, and the way out of that difficulty which was pro- 
posed in this country, was the use of self-recording in- 

I yS Meteorological Lectures. 

struments. We have had these instruments for many 
years, but at the present day we are no nearer uniformity 
than our fathers were a generation ago. 

We must only, therefore, submit to the inevitable, 
and make the best of what we can get. It is certain 
that the broad principles of our science have been laid 
down by men who did not look for such refinement in 
observation as is now demanded. 

I may perhaps be permitted to return over the 
ground trodden by my predecessors during the last five 
weeks, and give you a very brief account of some of 
these broad principles, which have already been ascer- 
tained with tolerable certainty, but which we are all en- 
deavouring to establish on a firmer basis. 

Firstly, as regards temperature, Mr. Laughton 
placed before you a large map showing the respective 
curves of yearly summer and winter temperature. The 
idea of drawing these curves we owe to A. von Hum- 
boldt ; the labour of carrying out the suggestion and 
making the subject his own, has been the lifelong work 
of Dove. As the general outcome of his researches on 
this head he proposed the charts which I exhibit, the 
abnormals of the globe. They were published by the 
British Association in 1853, and I have selected those 
for January and July. The general principle of these 
charts is, that if we conceive of the earth as a homo- 
geneous sphere with temperature decreasing uniformly 
from the equator to either pole, each parallel of latitude 
should have a definite temperature. 

The charts show you how widely the facts differ 

The Nature, Methods, &c., of Meteorology, i 79 

from this ideal state of things. I need only point out 
how strongly they bring out the contrasting influences 
on climate of continent and ocean. The greatest 
positive anomaly in January, or to speak in plain 
English, the most unnatural warmth in winter is that 
of the North Atlantic, due to the Gulf Stream ; and the 
shores of what the Americans call " Walrussia " are 
also much favoured, thanks to the Kuro Siwo of the 
Japanese seas. On the other hand, the two cold poles 
are shown in Arctic Asia and America. 

In July the Asiatic cold area is transferred to the 
Aleutian Islands, chilled by the efflux of cold water 
through Behrings' Straits, while the Northern Seas 
generally exhibit a defect of temperature, owing, as Mr. 
Laughton explained, to the high specific heat of water, 
which absorbs all the caloric it can get to lay it up 
against not a rainy, but a cold day. 

In the southern hemisphere we see in their winter 
the chill which falls along the coast of Peru, while the 
comparatively high latitude of the Australian colonies 
enables that continent to produce on its east coast a 
defect of as much as 1 0°. 

Those of you who have read Lyell's Principles of 
Geology will remember how, by shuffling the continents 
and oceans, like a pack of cards, he illustrated the 
possibility of the former existence on the earth of periods 
at which the tropical warmth of our cretaceous sea, and 
the piercing cold of the glacial epoch had respectively 

It is, however, hopeless to attempt to deal with 

1 80 Meteorological Lectures. 

temperature at greater length at present, and I shall 
now proceed to describe the rain chart which was 
merely touched upon by Mr. Symons. 

In it we notice how the sea-winds are in most cases 
the rain carriers to the coasts. The wettest regions in 
the globe are within or close to the tropics, where, at 
Gorgonia, near Panama, Dampier declared that the rain 
fell faster than he could drink it ; and where, at 
Cherrapoonjee, in the Khasia hills, not less than 600 
inches fell within six months. The falls on the western 
Ghauts do not come far short of this. When we look 
to our own shores we find at Stye Head and Sprinkling 
Tarn (which well deserves its name) an amount almost 
comparable with the deluges which visit tropical stations 
in the rainy season. 

The rainfall of a district is, however, mainl}- influ- 
enced by its proximity to the western coasts of its 
country, and by the lie of the mountain ranges by which 
it is traversed or encircled. 

A chart like that I show does not tell one hundredth 
part of what we have to learn about rain. Had we 
monthly charts, we could show on them the seasonal 
peculiarities and the relations of the rain to the pre- 
valent winds. Such a chart as we have is, however, a 
prodigious advance on those which were in use twenty 
years ago, on which the rain was shown in belts de- 
creasing from 1 00 inches in the torrid zone to 1 5 or 
less in the frigid. 

I shall, however, pass on with the remark that the 
question of the rainfall and the degree to which it may 

TJic Natttre, Methods, &c., of Meteorology. i8i 

be modified by human agency, is one which is now being 
considered by many European Governments. Now that 
it is found that rivers, such as the Danube, the Rhine, 
and the Volga, are silting up their beds, and that naviga- 
tion for scores of miles has been stopped by shoals, while 
at the same time the residents on the banks of the lower 
waters have been yearly more and more exposed to 
the ravages of floods, the governments have begun to 
intervene, as it appears that the only rivers which ex- 
hibit these effects are those whose banks and drainage 
basins have been recklessly despoiled of their forests. 
The authorities then step in and say that severe measures 
are required to ensure that the mischief shall not increase 
till it defies check. 

In more than one of our own colonies an ignorance 
of the principles on which, under ordinary circumstances, 
the rainfall of a district depends, has led to the excessive 
clearing of woodland and brush, whether it be for the 
"chena" rice cultivation of Ceylon, or thesugar plantations 
of Mauritius, and as a result in either case the utter sub- 
version of the natural hydraulic system of the country. 

Time would fail me were I to attempt to describe 
to you the state of our knowledge of the distribu- 
tion of barometrical pressure and of wind, which it is 
the great merit of Mr. Buchan to have established on a 
satisfactory basis. I must therefore pass on to say a few 
words about one of the questions of physical meteor- 
ology, as contrasted with climatology. 

This is the problem of the law of diurnal range of 
pressure and of the other elements. I need not remind 

1 8 2 Meteorologica I L edti res. 

you that temperature has a daily range, for when the 
sky is not obscured by fog the weather is at least 
warmer towards 2 P.M. than it is about sunrise. It may, 
however, surprise those who have not lived in tropical 
climates to learn that the barometer has a daily range 
showing maxima at about 9 A.M. and 9 P.M., and minima 
at about 3 A.M. and P.M., and that in the torrid zone, 
if this be interrupted, there must be some serious dis- 
turbance of the atmosphere brewing. In our latitudes 
the changes produced by storms, or, as they are called 
in scientific language, the non-periodic variations, are 
so large that they mask these minor oscillations, which 
are usually traceable only in very calm weather. 

The fact of this diurnal range being known, we 
have to search for its cause, and this is cosmical, as it 
affects the entire atmosphere. No satisfactory expla- 
nation of it has yet been given, but our late president 
Mr. Eaton, and Mr. Buchan, appear to have entered in- 
dependently on a line of inquiry which bids fair to be 
fruitful in results. 

You see from the diagram that there is a decided 
difference between the curves for Kew and Barnaoul, 
types respectively of insular and continental climates. 

Mr. Eaton has calculated these curves from seven 
British observatories, and he shows how the continental 
character gradually imprints itself on the course of the 
curves as we travel from the Atlantic seaboard towards 
the most continental station, Kew. He shows that this 
difference is related to the diurnal range of temperature. 
Where this is small, as at Valencia, we have the morn- 

The Natitre, Methods, &€., of Meteoj'ology. 183 

ing minimum more marked than that in the afternoon, 
while at Kew the reverse is the case. The other 
observatories show a gradual progression, in time and 
appearance, from ohe type to the other. 

Mr. Buchan has taken up the same inquiry on a 
more extensive scale, but with less rigorous demand for 
accuracy in the materials used, and he shows how the 
curve of diurnal range is affected in time and shape by 
proximity to the sea, and even to the great lakes of 
North America. 

This points out to us that the vapour present in the 
air is a factor which is not to be disregarded, and yet, 
as I have told you, our knowledge of this element is most 

A friend of mine, a most careful investigator, 
undertook, years ago, the discussion of barometrical 
diurnal range for all stations over the globe which 
could show honest, two-hourly observations, even for a 
few years. The labour of the calculation is complete, 
but he finds himself at a loss for information as to all 
the other elements, and no explanation of the phenome- 
non is possible without ample materials. 

Here, again, we ask for more, and for such inquiries 
as this we want the most refined instruments and the 
most scrupulous regard to accuracy of registration. 
Not only do we want the observations from stations on 
the ground, to speak in common parlance, but we long to 
sound the aerial ocean, by placing our instruments on 
mountain peaks, and, would it were possible! in balloons. 
We know that the curves of diurnal range, on Pike's 

184 Meteorological Lectti7^es. 

Peak (14,000 ft.) and at Mount Washington and the 
Puy de Dome (each 6000 ft.) differ materially from 
those formed on the plains below. 

Here is a noble field for future meteorologists to 
undertake, to devise some means of gaining intelligence 
of what is passing in the atmosphere, above our heads. 
Without such observations our knowledge of meteoro- 
logical processes cannot fail to be more or less incom- 
plete and unsatisfying. 

We now come to the concluding toast of the 
evening — our noble selves — the utility of meteorology, 
or of the Meteorological Society, to the general public. 
When jotting down the syllabus of this Lecture which 
is in your hands, I said that meteorology demanded a 
knowledge of other sciences, but it would have been 
more appropriate to say that the student of these 
sciences would be the better for meteorological know- 
ledge. It is hardly needful to urge this point further 
when we reflect what use our president has made of his 
meteorological acquirements in his long career. What 
engineer is there on the roll of the Institution of Civil 
Engineers who does not anxiously seek informa- 
tion from us on questions of water-supply, of tidal 
pressure on sea walls, or of wind force on Cleopatra's 
needle ? 

We may then ask ourselves, What are the ultimate 
uses of meteorology .■' and the answer to this is. They are 

Firstly, there is the strictly scientific use, the enabling 
us to gain a more intimate knowledge of the conditions 

The Nature, Methods, &c., of Meteorology. 185 

of our own atmosphere, and thereby of the earth as a 
member of the solar system. 

Secondly, however, its immediate practical use is the 
foretelling of weather. Shirk the admission how we 
may, it cannot be denied that the most abstruse discus- 
sions of meteorological data have hardly another object 
than the determination of the average conditions of the 
climate of each place, and of the amount of variability 
which may be anticipated in the march of each element. 
What is this but forecasting } 

In marine meteorology, again, we search laboriously 
for true mean values to indicate to the seaman where 
he may find " a fair wind and a favourable current," 
and what is this but implied prophecy .-' 

The fact is, there is not a profession, not a handicraft, 
not a process in animal or vegetable life, which is not 
influenced by meteorological changes, and there is not 
a human being to whom a knowledge of coming weather 
would not be of value. 

Had we, a quarter of a century ago, known the 
rigour of the Crimean climate, who would have dared to 
have sent out an army unprepared to meet the hardships 
of a Black Sea winter } Ask the physician at what 
price he would value the power of giving timely warn- 
ing of the coming of a " cold snap " to his patients. Ask 
the builders of London what they have lost in the last 
ten years by sudden frosts or unexpected downpours 
of rain. Above all things, go to the farmer and ask 
what he would freely pay to know at seed-time what 
weather he might really expect in harvest. 

1 86 Meteorological Lcctiircs. 

The roll is endless, — a knowledge of meteorology 
is of the very first importance in every stage of human 
life, civilised or uncivilised. 

Hence we learn the attractiveness of all the mani- 
fold attempts made to foretell the character of the 
weather and seasons, whether these be the venturesome 
storm warnings of our Transatlantic neighbours, or the 
sun-spot researches of Mr. Meldrum and Dr. Hunter. 

With reference to all such inquiries, my friend 
Captain Hoffmeyer has furnished me with an apt 
remark, " When the proper time arrives, a Kepler will 
be surely forthcoming to discover the laws by which 
our science works ; for us to endeavour to force the 
plant in its growth is hopeless." 

When we look at the prospects of meteorology, I 
think we need not despair. What though Pascal and 
Herschel have passed away with many lesser artificers 
of the goodly structure of our science ; while Dove 
and Sabine, though still among us, have long ceased to 
work ! Yet, if we look around and see men like Hann, 
Mohn, Wojeikoff, and though last not least, our own 
Buchan, we may challenge any one to say that the gifts 
of patient investigation and of far-seeing generalisation 
are not still present in our midst. 

May, 1879. 



S5, o la: ^^ i^ I nsr G- ck-oss, 





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VIVIAN.— NOTE.S of a TOUR in AMERICA. From August 7th to Novem- 
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WALIiACE.— AUSTRALASIA. (Stanford's Compendhjm of Geogkapht 
AND Travel.) Based on Hellwald's 'Die Krde und Ihre Vollcer.' Edited and 
Extended by A. R. Wallaci:, F.R.G.S., Author of ' The Malay Archipelago,' 
' Geographical Distribution of Animals,' &c. With Ethnological Appendix by 
A. H. Keane, B.A. Twenty Maps and Fifty-six Illustrations. Large post 8vo, 
cloth, 21s. 

MINERAL DEPOSITS. The Laws which Regulate the Deposition of Lead 

Ore in Mineral Lodes. Illustrated by an Examination of the Geological 
Structure of the Mining Districts of Alston Jloor. By \V. AVallace. With Map 
and numerous Coloured Plates. Large demy 8vo, cloth, 25s. 

QUIBO and POTARO RIVERS. With an Account of a Visit to the Kateteur 
tails. By Lieut. -Colonel Webber, 2nd West India Regiment. With Map and 
Frontispiece. Crown 8vo, clotli, 4s. 6d. 

By Dr. E. P. Wilkins, F.(;.S., &c. With Ptelief Map of the Island, coloured 
geologically. Super-royal 8vo, cloth, 7s. 6d. 

WILiLIAMS.— Through NORWAY with a KNAPSACK. A New and Im- 
proved Edition. \Vith Notes on Recent Changes, suggested by a Recent revisit. 
By W. Williams, F.R.A.S., F.C.S., &c., Author of ' The Fuel of 
the Sun,' &c. With Map. Crown Svo, cloth, 6s. 

Through NORWAY with LADIES. By W. Mattieu Williams, F.R.A.S. 

F.O.S., Author of • Through Norway with a Knapsack.' With Map and Hlus 
trations. Crown Svo, cloth, 12s. 

With Map. Fcap.' svo, cloth, 2s. 


Map, and Plan of Exeter Cathedral. Fcap. Svo, cloth, 2s. 

YOITNG-.- THE TAVO VOYAGES of the ' PANDORA' in 1875 and 1876. Bj-. 
Sir Allen Young, R.N.R., F.R.G.S., F.R.A.S., &c., Commander of the Expedi- 
tion. Super-royal Svo, cloth, with Two large folding Maps, and Nine full-page- 
lUustrations, 10s. 6d. 

Edward Stanford, 55, Charing Cross, London. 

fikarg 0r Mall Paps. 

ETTROPE. — Scale, 50 miles to an inch; size, 65 inches by 58. Coloured and 
mounted on linen, in morocco case, 31. 13*. 6d. ; on roller, varnished, 31. ; spring 
roller, 61. 

ENGLAND and "WALES.— Scale, 5 miles to an inch ; size, 72 inches by 84- 
Coloured, 2l. 12s. 6c;. ; mounted on linen, in morocco case, 31. 13s. 6rf. ; on roller, 
yaraished, 4/. is. ; spring roller, 61. 6s. 

LONDON and its STJBUIIBS.— On the scale of six inches to a mile: 
constructed on the basis of the Ordnance block plan. Price, in sheets, plain, 
21s. ; coloured, in a portfolio, 31s. 6d. ; mounted on linen, in morocco case, or on 
roller, varnislied, 21. 15s. ; on spring roller, 5l. 5s. Single sheets, plain. Is. ; 
coloured. Is. 6d. A Key Map may be had on application, or per post for one 

SCOTLAND. — Scale, five miles to an inch; size, 52 inches by 76. Coloured, 
42s. ; mounted on linen, in morocco case, 31. 3s. ; on roller, varnished, 31. 13s. 6d.; 
spring roller, 51. 5s. 

IRELAND. — Scale, 5 miles to an inch; size, 43 inches by 58. Coloured, four 
sljeets, 25s.; mounted, in case, 35s.; on roller, varnished, 21. 2s.; on spring 
roller, il. is. 

ASIA.— Scale, 110 miles to an inch; size, 65 inches by 58. Coloured and 
mounted on linen, in morocco case, 31. 13s. 6d. ; on roller, varnished, 31. ; spring 
roller, 61. 

AFRICA.— Scale, 94 miles to an inch; size, 58 inches by 65. Coloured and 
mounted on linen, in morocco case, 31. 13s. 6d. ; on roller, varnished, 3/. ; spring 
roller, 61. 

NORTH AMERICA.— Scale, 83 miles to an inch; size, 58 inches by 65. 
Coloured and mounted on linen, in morocco case, 3/. 13s. 6d.; on roller, 
varnished, 31. ; spring roller, 61. 

CANADA. — Scale, 16 miles to an inch; size, 96 inches by 54. Eight Coloured 
Sheets, 21. 12s. 6d.; mounted, in case, 31. 13s. 6d. ; on roller, varnished, 41. 4s.; 
spring roller, 81. 


miles to an inch ; size, "2 inches by 56. Coloured and mounted on linen, in 
morocco case, 31. 13s. 6(f. ; on roller, varnished, 3l. ; spring roller, 61. 

SOUTH AMERICA.— Scale, 83 miles to an inch; size, 58 inches by 65. 
Coloured and mounled on linen, morocco case, 31. 13s. 6d: on roller, varnished, 
31. ; spring roller, 61. 

AUSTRALASIA.— Scale, 64 miles to an inch; size, 65 mches by 58. 
Coloured and mounted on linen, morocco case, 31. 13s. 6d. ; on roller, varnished, 
3^; spring roller, 61. 

AUSTRALIA.— Scale, 26 miles to an inch; size, 8 feet 6 inches by 6 feet 
6 Inches. In Nine Sheets, coloured, 21. 12s. 6d. ; mounted, in morocco case, 
or on roller, varnished, il. is. ; on spring roller, 11. Is. 

Edward Stanford, 55, Charing Cross, London. 


(Bmnid Slaps. 

latest l-'olitical Boundaries, tlie Railways, the Submarine Telegraphs, &c. Scale, 
150 miles to an inch; size, 36 inches by 33. Fully coloured and mounted on 
linen, in case, 10s. ; on roller, varnished. Us. 

containing all the Railways, with their Stations. The principal roads, the 
rivers, and chief mountain ranges are clearly delineated. .Scale, 24, miles to 
an inch ; size, 47 inches by 38. Sheets, plain, 10s. ; coloured, 12s. ; mounted on 
linen, in case, 16s. 

AUSTRIAN EMPIRE. By J. Akeowsmith. Scale, 28 miles to an inch; 
size, 26 inches by 22. sheet, coloured, 3s. ; moimted in case, 5s. 

DENMARK and ICELAND. By J. Arrowsmith. Scale, 13 miles to 
an inch; size, 22 inclies by 26. .Sheet, coloured, 3s. ; mounted in case, 5s. 

FRANCE, in DEPARTMENTS. With a Supplementary Map, divided 
Into Provinces, and a Map of the Island of Corsica. By J. Arkowsmith. Scale, 
31 miles to an inch; size, 22 Inches by 26. Sheet, coloured, 3s. ; mounted in 
case, 5s. 

G-ERM ANY. By J. Arrowsmith. Scale, 25 miles to an inch ; in two sheets, 
size of each, 22 inches by 26. Price of each, coloured sheet, 3s. ; mounted, in 
case, 5s. ■ 

ITALY, including Sicily and the Maltese Islands. By J. Arkowsmith. Scale, 
20 miles to an inch ; in two sheets, size of each, 22 inches by 26. Price of each, 
coloured, 3s. ; mounted in case, 5s. 

NETHERLANDS and BELGIUM, including Luxembourg and the 

Country to the East as far as the Rhine. By J. Arrowsmith. Scale, 13 miles 
to an inch ; size, 22 inches by 26. Sheet, coloured, 3». ; mounted in case, 5s. 

RUSSIA and POLAND, including Finland. By .T. Arrowsmith. Scale, 
MU miles to an inch ; size, 22 inches by 26. Sheet, coloured, 3s. ; mounted in 
case, 5s. 

SPAIN and PORTUG-AL. By J. Arrowsmith. Scale, 30 miles to an 
inch ; size, 26 inches by 22. Sheet, coloured, 3s. ; mounted in case, 5s. 

SWEDEN and NORWAY. By J. Arhow.smith. Scale, 35 miles to an 
inch ; size, 22 inches by 26. Sheet, coloured, 3s. ; mounted In case, 5s. 

SWITZERLAND. By .1. Arrowsmith. Scale, lOi^ miles to an inch; size, 
26 inches by 22. Sheet, coloured, 3s. ; mounted in case, 5s. 

TURKEY in EUROPE, including the Archipelago, Greece, the Ionian 
Islands, and the South )iart of Dalmatia. By J. Arrowsmith. Scale, 40 miles 
to an inch ; size, 22 inches bj' 26. Sheet, coloured, 3s. ; mounted in case, 5s. 

Edward Stanford, 55, Charing Cross, London. 


BRITISH ISLES.— NEW WALL MAP. Constructed on the basis of the 
Ordnance Survey, and distinguishing in a clear manner the Cities, County and 
Assize Towns, Municipal Boroughs, Parliamentary Representation Towns which 
are Counties of themselves. Episcopal Sees, Principal Villages, &c. The 
Railways are carefully laid down and coloured, and the Map from its size is 
well suited for Public OfBces, Institutions, Reading-Rooms, Railway Stations, 
good School-Rooms, &c. Scale, 8 miles to an inch; size, 81 inches by 90. 
Price, coloured, mounted on mahogany roller, and varnished, 31. 

ISLKS, and part of France, Scale, 22 miles to an inch ; size, 31 inches by :iS. 
Price, coloured in sheet, 6s. ; mounted on linen, in case, 9s. ; or on roller, 
varnished, 15s. 

Constructed to show the Correct Relation of the Physical Features. Size, 
50 inches by 58; scale. Hi miles to 1 inch. Price, mounted on roUers and 
varnished, 21s. 


MAP of ENGLAND and WALES. In 24 sheets (sold separately). Con- 
structed on the basis of the trigonometrical survey. By J. Arrowsmith. Scale, 
3 miles to an inch ; size of each sheet, 20 inches by 28. Price, plain. Is. ; 
mounted in case, 2s. 6d. ; coloured. Is. 6d. ; mounted in case, 3s. Size of the 
complete map, 114 inches by 128. Price, plain, in case or portfolio, 11. 5s.; 
coloured, in aise or portfolio, 11. 8s. ; mounted on cloth to fold, in case, coloured, 
41. 4s.; on canvas, roller, and varnished, U. 14s. 6d. : on spring roller, i)l. 9s. 

LAND and WALES. With the Railways very clearly delineated; the Cities 
and Towns distinguished according to their Population, &c. Scale, 15 miles to 
an inch ; size, 28 inches by 32. Coloured and mounted on linen, in case, 5s.; 
or on roller, varnished, 8s. 

ENGLAND and "WALES— WALL MAP. Scale, 8 miles to an inch; 
size, 50 inches by 58. Price, mounted on mahogany roller, varnished, 21s. 

SCOTLAND.— NEW WALL MAP, showing the Divisions of the Counties, 
the Towns, Villages, Railways, &c. Scale, 8 miles to an inch ; size, 34 inches 
by 42. Price, coloured, mounted on mahogany roller, and varnished, 12s. 6d. 

SCOTLAND, in COUNTIES. With the Roads. Rivers, &c. By J. 
Arrowsmith. Scale, 12 miles to an inch; size, 22 inches by 26. Sheet, 
coloured, 3s. ; mounted in case, 5s. 

IRELAND, in COUNTIES and BARONIES, on the basis of the 
Ordnance Survey and the Census. Scale, s miles to an inch ; size, 31 inches 
by 38. On two sheets, coloured, 8s. ; mounted on linen, in case, 10s. Gd. ; on 
roller, varnished, 15s. 

IRELAND.— NEW WALL MAP, showing the divisions of the Counties, all 
the Towns, Principal Villages, Railways, &c. Scale, 8 miles to an inch ; size, 
34 inches by 42. Price, coloured, mounted on roller, varnished, 12s. 6d. 

IRELAND, in COUNTIES. With the Roads. Rivers, &c. By J. 
Arrowsmith. Scale, 12 miles to an inch; size, 22 inches by 26. Sheet, 
coloured, 3s. ; mounted in case, 5s. 

Edward Stanford, 55, Charing Cross, London. 



MODERN LONDON and its STJBURBS, extending from Hanipstead 
to the Crystal Palace, and from Hammersmith Bridge to Greenwich ; showing 
all the Railways and Stations, the Roads, Footpaths, &c. Scale, 6 inches to the 
mile ; size, 5 feet by 6. On six large sheets, 25s. ; mounted on linen, in case, or 
on roller, varnished, 42s. 

COLLINS' STANDARD MAP of LONDON. Admirably adapted 
for visitors to the City. Scale, 4 inches to a mile ; size, 34^ inches by 27. 
Price, plain, in case, Is. ; coloured, Is. 6d. ; mounted on linen, ditto, 3s. 6d. ; 
on roller, varnished, 7s. 6d. 

METROPOLI.S. Scale, 3 inches to a mile ; size, 36 inches by 25*. Price, 
plain sheet, 3s. 6d. ; coloured. 5s. ; mounted on linen, in case, 7s. 6iJ. ; on roller, 
varnished, 10s. ed. With continuation southward beyond the Crystal Palace, 
plain sheet, 5s.; coloured,; mounted on linen, in case, Us.; on roller, 
varnished, 15s. 

ENVIRONS. Scale, 1 inch to a mile; size, 24 inches by 26. Price, coloured 
and folded, Is. ; mounted on linf-n, in case, 3s. 

of LONDON, showing all the Stations on the 'Inner,' 'Middle,' and 'Outer' 
Circles of the Metropolitan Underground Railways, with the principal Streets, 
Parks, Public Buildings, Places of Amusement, &c. Size, 37 inches by 24. 
Coloured, and folded in cover, 6d. 

ENVIRONS, showing the boundary of the Jurisdiction of the Metropolitan 
Board of Works, the Parishes, Districts, Railways, &c. Scale, 2 inches to a 
mile ; size, 40 inches by 27. Price, in sheet, 6s. ; mounted on linen, in case, 9s. ; 
on roller, varnished, 12s. 

ENVIRONS. Scale, 2 inches to a mile; size, 36 inches by 28. The main roads 
out of London, the Minor Roads and Footpaths in the Environs, the Railways 
completed and in progress, are carefully defined, Price, sheet, 4s. ; coloured, 
5s. 6d. ; mounted on linen, in case, 8s.; or on roller, varnished, 14s. 

including twenty-five miles Irom the Metropolis. Scale, f of an inch to a mile; 
size, 36 inches by 35. This Map includes the whole of the County of Middlesex, 
with parts of the Counties of Surrey, Kent, B^sex, Herts, Bucks, and Berks. 
Price, on one large sheet, coloured, 8s. ; mounted, in case, 10s. ; on roller, var- 
nished, 14s. 

LONDON. Scale, 1 inch to a mile; size, 43 inches by 32. Price, sheet, plain, 4s.; 
coloured 5s. 6d. ; mounted on linen, in case, 8s. ; or on roller, varnished, 14s. 

TAVELVE MILES round LONDON. Scale, 1 inch to a mile; size, 25 IncheB 
by 25. Price, plain, folded in case, 2s. Gd. ; coloured, ditto, 3s. 6d. ; mounted on 
linen, ditto, 5s. 6d. 

Edward Stanford, 55, Charing Cross, London. 


GENERAL MAP OF ASIA.— By J. Arrowmiith. Scale, 300 miles to 
an inch ; size, 26 inches by 22. Sheet, coloured, 3s. ; mounted, In case, 5s. 

NORTHERN ASIA, including Siberia, Kamtschatlja, Japan, Mantchooria, 
Jlongolia, Tchoongaria, Tibet, and the Himalaya Mountains. By J. Akrow- 
sitiTH. Scale, 170 miles to an inch ; size, 26 Inches by 26. Sheet, coloured, 4s.; 
mounted, in case, 7s. 

Teheran, Khiva, Bokhara, Koljan, Yarkand, Kabul, Herat, &c. Scale, 110 miles 
to an inch ; size, 22 inches by 1 7. Coloured sheet, 2s. 6d. ; mounted, in case, 5s. 

ASIA MINOR, &C. (TORKEY in ASIA). With portions of Persia, the 
Caspian Sea, and the Caucasian Mountains. By J. Akrowsmith. Scale, 55 
miles to an inch; size, 26 inches by 22. Sheet, coloured, 3s.; mounted, in 
case, 5s. 

Present Divisions of the Country according to the most Recent Surveys. Scale, 
86 miles to an inch : size, 29 inches by 33. Coloured, 6s. ; mounted on linen, in 
case, 8s.; on roller, varnished, lis. 

INDIA.— MAP of INDIA. By J. Aerowsmith. Scale, 90 miles to an inch; 
size, 22 inches by 26. Sheet, coloured, 3s. ; mounted in case, 5s. 

CEYLON.— MAP of CEYLON. Constructed from a Base of Triangulations and 
corresponding Astronomical Observations. By Major-General John Fraseh, 
late Deputy-Quarterraaster-General. Reconstructed by John ARROwsMrTH. 
Scale, 4 miles to an inch ; size, 52 inches by 78. Eight sheets, coloured, 21. 5s. ; 
mounted, in case, 31. 13s. 6d.; on roller, varnished, il. 4s.; spring roller, 
61. 16s. 6d. 

CEYLON.— COFFEE ESTATES of CEYLON. Map showing the Position of the 
Coffee Estates in the Central Province of Ceylon. By J. Akrowsmith. Size, 
15 inches by 20. Sheet, coloured, 3s. ; mounted, in case, 5s. 

BURMAH, &C. — A Map showing the various Routes proposed for connecting 
China with India and Europe through Burmah, and developing the Trade of 
Eastern Bengal, Burmah, and China. Prepared under the direction of John 
OoiLvr Hay, F.R.G.S. Scale, 33 miles to an inch; size, 27 inches by 32. 
Coloured, 3s. ; mounted, in case, 5s. 

various MSS., and other Documents. By J. Akkowsmith. Scale, 24 miles to 
an inch ; size, 26 inches by 22. Sheet, coloured, 3s. ; mounted, in case, 5s. 

CHINA.— MAP of CHINA. By J. Arrowsmith. Scale, 90 miles to an inch ; 
size, 26 inches by 22. Sheet, coloured, 3s. ; mounted, in case, 5s. 

and JAPAN, with the Adjacent Parts of British India, Asiatic Russia, Buniiab, 
&c. Scale, 110 miles to an inch ; size, 38 inches by 24. One sheet, full coloured, 
8s. ; mounted on linen, in case, 10s. 6d. ; on roller, varnished, 14s. 

Edward Stanford, 55, Charing Cross, London. 



GrENERAIi MAP of AFRICA.— By J. Arrowsmith. Scale, 260 mHes 
to au inch ; size, 22 inches by 26. Sheet, coloured, 3s. ; mounted, in case, 5s. 

EG-YPT.— MAP of EGYPT. Compiled from the most authentic materials, and 
founded on the best Astronomical Observations. By Colonel AV. M. Leake, 
R.A., LL.D;, F.R.S. Scale, 10 miles to an inch; size, 34 inches by 52. Two 
she^s, coloured, 21s. ; mounted, in case, 28s. ; on roller, varnished, 36s. 

EGYPT.— MAP of EGYPT: including the Peninsula of Mount Sinai. By 
J. AituowsMiTH. Xen- Edition. .Scale, 26 miles to an inch; size, 22 inches by 
26. .Sheet, coloured, 3s. ; mounted, in case, 5s. 

eluding the Coast of Guinea, and the Isle of Fernando Po, on the South, and the 
Western parts of Egypt and Darfur, on the East. By J. Areowsmith. Saile, 
130 miles to an inch ; size, 26 inches by 22. Sheet, coloured, 3s. ; mounted, in 
case, 5s. 

AFRICA (SOUTH?.— MAP of SOUTH AFRICA to 16 deg. South Latitude. 
By Hf.nkt Hall, Draughtsman to the Royal Engineers, Cape Town. Scale, 50 
miles to an inch ; size, 34 inches by 28. Two sheets, coloured, 10s. 6d. ; 
mounted on linen, in case, 13s. 6d.; on roller, varnished, 15s. 

AHIICA. Compiled by Henet Hall. Scale, 25 miles to an inch; 'size, 26 
inches by 22. Sheet, 4s. ; mounted on linen, in case, 6s. 

Comprising Guinea and the British Possessions at Sierra L^one, on the Gambia, 
and the Gold Co;ibt, &c. By .J. Arrowsmith. Scale, 50 miles to an inch. Two 
coloured sheets ; size of each, 22 inches by 26, 6s. Mounted, in case, lOj. 

AFRICA, Cape Colony, Xatal, &c. By Henrt Hat.l. .Scale, 50 miles to an 
inch; size, 29 inches by 17. Sheet, price 4s. 6d. ; mounted, in case, 6s. 6d. 

FRONTIER of the CAPE COLO.VY. Compiled by Henrt Hall. Scale, 
8 miles t'> an inch ; size, 40 in -hes by 38. Sheets, 18s. 6d. ; mounted on linen, 
in case, 25s.; on roller, varnished, 31s. 6d. 

NATAIi.— A MAP of the COLONY of NATAL. By Alexandeb Mair, Land 
Surveyor, Natal. Compiled from the Diagrams and General Plans in the 
Surveyor-General's Office, and from Data furnished by P. C. Sctherland, Esq., 
M.D., F.R.S., Surveyor-General. Scale, 4 miles to an inch ; size, 54 inches by 80. 
Coloured, Four Sheets, 21. 5s. ; mounted, in case, or on rollers, varnished, 31. 

NATAL.— MAP of the COLONY of NATAL. Compiled in the Surveyor- 
Generals Office. Size, Hi Inches by 14J. Sheet, coloured. Is.; momited, in 
case, 2s. 6d. 

NUBIA and ABYSSINIA, including Darfur, Kordofan, and part of Arabia. 
By J. AKrtowsMiTH. Scale 65 miles to an inch; size, 26 inches by 22. Sheet, 
coloured, 3s. ; mounttd, in case, 5s. 

Edward Stanford, 55, Charing Cross, London. 


56tii Parallel North Latitude, showing the New Gold Fields of Omineca, the 
most recent discoveries at Cariboo and other places, and tlie proposed routes for 
the Inter-Oceanic Railway. Scale, 25 miles to an inch ; size, 39 inches by 27. 
Price, in sheet, coloured, 7s. 6d. ; or mounted on linen, in case, 10s. 6d. 

CANADA.— MAP of UPPER and LOWER CANADA, New Brunswick, Nova 
Scotia, Prince Edward's Island, Cape F«reton Island, Newfoundland, and a large 
portion of the United States. By J. Abrowsmith. Scale, 35 miles to an inch ; 
size, 40 inches by 26. Two sheets, cotoured, 6s. ; mounted, in case, 10«. ; on 
roller, varnished, 15s. 

with Canada, New Brunswick, &c. Scale 54^ miles to an inch ; size, 57 inches 
by 36. Two sheets, coloured, 21s. ; case, 25s. ; on rollers, varnished, 30s. 


STATES. Scale, 90 mites to an inch ; size, 40 inches by 25. Coloured sheet, 
7s. 6(i. ; mounted, in case, lOs. 6d. ; on roller, varnished, 15s. 

UNII'ED STATES. Scale, 120 miles to an inch; size, 29 inches by 17i. Two 
sheets, coloured, 4s. id. ; mounted on linen, in case, 6s. 6d. 

. including the States of Guatemala, Salvador, Honduras, Nicaragua, and Costa 
Rica. Scale, Smiles to an ioch; site, 40 inches by 27. Sheet, 7s. 6(Z.; mounted 
on liuen, in case, lOs. 6rf. ; on roller, varnished, 14s. 

Brigadier-General Pedro Gakcia Conde. Engraved from the Original Survey 
made by order of the Me.\ican Government. Size, 50 inches by 37. Sheets, 
price, lus. 6d. ; mounted on linen, in case, 18s. 

BERMUDAS.— MAP of the BERMUDAS. Published by direction of His 
E.\cpllency Major-General J. H. Lefboi, C.B., R.A., Governor and Commander- 
in-Chief of tke Bermudas. Scale, 2^ miles to an inch; size, 62 inches by 63. 
Mounted, in case, or on poller, varnished, 21s. 

Colonies in possession of the various European Powers. By J. Aekowsjjith. 
Scale, 90 miles to an icch ; size, 26 inches by 22. Sheet, coloured, 3s. ; mounted, 
ifl case, 5s. 

Thomas Haekison, Government Surveyor, Kingston, Jamaica, under the direc- 
tion of Major-General J. R. Mann, U.E., Director of Roads and Surveyor-General. 
Scale, 2i miles to an inch ; size, 64 inches by 27. Mounted, in case, or on roller, 
varnished, 21s. 

BARBADOES. — Topographical Map, based upon Mayo's Original Survey in 
1721, and corrected to the year 1846. By Sir Robeet H. Schombdegh, K.R.E. 
Scale, 2 miles to an inch; size, 40 inches by 50. Two sheets, coloured, 21s.; 
mounted, in case, 28s. ; on roller, varnished, 37s. 

Edward Stanford, 55, Charing Cross, London. 


ATJSTRAIjASIA. — ^Thls Map inclodes Australia, Tasmania, New Zealand, 
lionieo, and the Malay Archipelago. The Natural Features are accurately and 
distinctly represented, and the Tracts of all the Australian Travellers up to the 
present time are laid down. The Divisions of the British Possessions into 
Provinces and Counties are shown. Scale, 86 miles to an indi; size, 58 inches 
by 50. Price, mounted on linen, on roller, varnished, 13s. 

AUSTRALIA. — With all the Recent Explorations, Tracts of the Principal 
E.xplorers, the P>oads, Railways, Telegraphs, and Altitudes. Originally Drawn 
by, and Engraved under the immediate superintendence of, the late John 
Areowsmith. Revised and Corrected to present date. Scale, 80 miles 4o an 
inch ; size, 44 inches by 26. Sheets, coloured, 6s. ; mounted in case, 10». 

"WESTERN ATJSTRAIilA.— With Plans of Perth, Fremantle, and (Juild- 
ford. From the Surveys of John Septimus Roe, Esq., Surveyor-General, and from 
other Official Documents in the Colonial Office and Admiralty. By J. Arrow- 
smith. Scale, 16 miles to an inch ; size, 40 inches hy 22. Two rfieets, coloured, 
6s. ; in case, 10s. 

SOUTH AUSTRALIA.— Showing the Division into Counties of the settled 
portions of the Province. With Situation of Mines of Copper and Lead. From 
the Surveys of Capt. Fronie, R.E., Surveyor-General ot the Colony. By J. 
Arrowsm'ith. Scale, 14 miles to an incla ; size, 22 inches by 26. Sheet, 
coloured, 3s. ; in case, 5«. 


gUEENSI>AN'l) (North-Eastern Australia): Compiled from the most reli- 
able Authorities. Scale, 64 miles to an inch ; size, 18 inches by 23. In sheets, 
coloured, 2s. 6d. ; mounted on linen, in case, 4s. M. 

Showing all the Roads, Rivers, Towns, Counties, Gold Diggings, Sheep and 
Cattle Stations, &c. Scale, 20 miles to an inch; size, 31 inches by 21. In 
sheet, 2s. 6d. ; or mounted on linen, in case, 4s. 6d. 

NEW ZEALAND.— With aU Recent Topographical Information, New Ad- 
ministrative iJivisioiis, Railways, Submarine I'elegrapbs, Ac. Size, 24 inches 
by 42 ; scale, 25 miles to an inch. Price, mounted in case or on roller, var- 
nished, 9s. 

from the must recent Documents. Scale, 64 miles to an inch ; size, 17 inches 
by 9. Full-coloured, in sheet, 2s. ; mounted on linen, incase, 3s. 6ci. 

NEW ZEALAND.— From Official Documents. By J. Arrowsmith. Scale, 
38 miles to an inch; size, 22 inches by 26. Sheet, coloured, 3s.; mounted, in 
case, 5s. 

TASMANIA (Van Diemen's Land).— From MS. Surveys in the 
Colonial Office, and in the Van Diemen's Land Company's Office. By J. Arrow- 
ssiiTH. Scale, lOJ- miles to an inch ; size, 22 inches by 26. Sheet, coloured, 3s. ; 
mounted in case, 5s. 


^cokgrcal ||taps. 

Professor A. C. Ramsat, LL.D., F.R.S., Director-General of the Geological 
Surveys of the United Kingitom. Scale, Hi miles to an inch; size, 50 inches 
by 5S. Mounted on rollers, varnished, 42s. 

ISLbiS. Compiled under the Superintendence of E. Best, H.M. Geological 
Survey. Scale, 25 miles to an inch; size, 23 inches by 29. 

ENGrliAND and WALES. By Andrew C. Ramsat, LL.D., F.R.S., and 
G.S., Director-General of the Geological Surveys of Great Britain and Ireland, 
and Professor of Geology at the Royal School of Mines. This Map shows all 
the Railways, Roads, &c., and when mounted in case, folds into a convenient 
pocliet size, making an excellent Travelling Map. Scale, 12 miles to an inch ; 
size, 36 inclies by 42. Fourth Edition, with Corrections and Additions. Price, in 
sheet, 11. 5s. ; mounted on linen, in case, IJ. 10s. ; or on roller, varnished, IL 12s. 

ENGLAND and WALES. Showing the Inland Navigation, Railways, 
Roads, Minerals, &c. By J. ARROWSMrrn. Scale, 18 miles to an inch ; size, 
22 inches by 26. One sheet, I2s. ; mounted in case, 15s. 

EAST of ENGLAND and Part of France; including the Weald and the Bas 
Boulonnais. By William Toplet, F.G.S., Geological Survey of England and 
'W^ales, and J. B. Jordan, Mining Record Office. Scale, 4 miles to an inch 
horizontal, and 2,400 feet to an inch vertical. Coloured and varnished in blaclc 
frame, to hang up, 51. ; or pacised in case for safe transit, 51. 5s. 

LONDON and its ENVIRONS. Scale, 1 inch to a mile; size, 24 inches 
by 26. Compiled from various authorities by J. B. Jordan, Esq., of the 
Mining Record OfBce. Price, folded in cover, 5s. ; mounted on linen, in case, 
7s. 6(1. ; or on roller, varnished, 9s. 

IRELAND. Founded on the Maps of the Geological Survey of Sir Richard 
Griffith and of Professor J. B. Jukes. By Edward Hull, M.A., F.R.S., 
Director of H.M.'s Geological Survey of Ireland. Scale, 8 miles to an inch ; 
size, 31 inches by 38. Price, in sheets, 25s. ; mounted on linen, in case, 30s. ; 
on rollers, varnished, 32s. 

Compiled by E. J. Dunn from personal observations, combined with those of 
Messrs. A. G. and T. Bain, Wtlie, Athekstone, Pinchin, Sutherland, ami 
Button. Scale, 35 miles to an inch; size, 34 inches by 28. One sheet, 10s.; 
mounted in case, 13s. 6d.; on roller, varnished, 16s. 

»rS. Including .__ 

By Sir W. E. 

Logan, F.R.S., &c.. Director of the Geological Survey of Canada. Scale, 25 miles 
to an inch; size, 102 inches by 45. On eight sheets, 31. 10s. ; mounted on lineu, 
on roller, varnished, or in two parts to fold in morocco case, 51. 5s. 

Alexander Murray, F.G.S., assisted by James P. Howlet, and Drawn by 
Robert Barlow. Scale, 25 miles to an inch; size, 26 inches by 26. One 
Sheet, 10s. ; mounted in case, 12s. ad. 

Edward Stanford, 55, Charing Cross, London. 



Prepared under the direction of the Society for Promoting Christian Knowledge 
and of the National Society, are patronized by Her Majesty's Government 
for the Army and Navy Schools, the Commissioners of National Education for 
Ireland, the School Boards of London, and of all the principal Provincial 
towns. The Series comprises the following Maps: — 
SPHERE.— Two distinct Maps. Size, each 50 inches by 58. Price of each, 
momited on roller, varnished, 13s. ; the two mounted together, 268. 
EUROPE.— Scale, 65 miles to an Inch; size, 50 inches by 58. Price, mounted on 

roller, varnished, 13s.' 
BRITISH ISIiES.— Scale, 8 mUes to an inch ; size, 75 inches by 90. Moujted 

on roller, varnished, price 42s. 
BRITISH ISLES.— Scale, ll^ miles to an inch ; size, 50 inches by 58. Price, 

mounted on roller, varnished, 13s. 
ENGLAND and WALES— Scale, 8 miles to an inch; size, 50 inches bf 58. 

Price, mounted on rollir, varnished, 13s. 
SCOTLAND and IRELAND.— Separate Maps. Scale, 8 miles to an inch ; 

size, 34 inches by 42. lYice of each, mounted on roller, varnished, 9s. 
ASIA. — Scale, 140 miles to an inch ; size, 50 inches by 68. Price, mounted on 

roller, varnished, 13i. 
HOLY LAND.— Scale, 4* miles to an inch; size, 50 inches by 58. Price, 

mounted on roller, varnished, 13s. 

OLD TESTAMENT. Scale, 8 miles to an inch; size, 34 inches by 42. Price, 

mounted on roller, varnished, 9s. 

NEW TESTAMENT. Scale, 7 miles to an inch ; size, 34 inches by 42. Price, 

mounted on roller, varnished, 9s. 
ACTS and EPISTLES.— MAP of the PLACES mentioned in the ACTS and 

the EPISTLES. Scale, 57 miles to an inch; size, 34 inches by 42. Price, 

mounted on roller, varnished, 9s. 

PENINSULA of SINAI, the NEGEB, iuid LOWER EGYPT. Scale, 10 miles 

to an inch; size, 42 inches by 34. Price, mounted on roller, varnished, 9s. 
INDIA.— Scale, 40 miles to an Inch; size, 50 inches by 58. Price, mounted on 

roller, varnished, 13s. 
AJFRICA.— Scale, 118 miles to an Inch ; size, 50 inches by 58. Price, mounted 

on roller, varnished, 13s. 
NORTH AMERICA.— Scale, 97 miles to an inch; size, 50 inches by 58. 

Price, niount'il on roller, varnished, 13s. 
SOUTH AMERICA.— Scale, 97 miles to an inch; size, 50 Inches by 58. 

Price, mounted on roller, varnished, 13s. 
AUSTRALASIA.— Scale, 86 miles to an inch ; size, 58 inches by 50. Price, 

mounted on roller, varnished, 13s. 
AUSTRALIA.— Scale. 86 miles to an inch; size, 42 inches by 34. Price, 

mounted on roller, varnished, 9s. 
NEW ZEALAND.— Scale, 25 miles to an inch ; size, 42 inches by 34. Price 

mounted on roller, varnished, 9s. 

Edward Stanford, 55, Charing Cross, London. 


Published under the direction of the Committee of General Literature and Kduca- 
tion appointed by the Society for Pkomotikg Chkistian Knowledge, and 
of the National Society. 

These New Maps are accurately Coloured in Political Divisions; they retain all the 
charaderistic boldness of the larger Series, and are specially suitable/or ^niall 


WESTERN HEMiSPHKRK. Two separate Maps. Size of each map, 27 

inches by 32. Price, coloured and mounted on roller, varnished, 6s. each; 

coloured sheet, 2s. 6d. 

*»* The two Hemispheres can be had mounted as one map ; size, 54 inches by 32. 

Price, coloured, on roller, varnished, 12s. 

EUROPE. — Size, 32 inches by 27. Coloured and mounted on roller, varnished, 

6s. ; coloured sheet, 2s. 6d. 
ASIA.— Size, 32 inches by 27. Coloured and mounted on roller, varnished, 6s ; 

coloured sheet, 2s. 6d. 
INDIA. — Size, 27 inches by 32. Coloured and mounted on roUer, varnished, 

6s.; coloured sheet, 2s. 6d, 

Size, 27 inches by 32. Coloured and mounted on roller, varnished, 6s. ; 

coloured sheet, 2s. 6d. 

OLD TESl'AMENT. Size, 17 inches by 22. Coloured and mounted on roller, 

varnished, 4s. ;* on millboard, varnished, 3s. 6d. ; coloured sheet. Is. 6d. 

NEW TESTAMENT. Size, 17 inches by 22. Coloured and mounted on 

roller, varnished, 4s. ;* on millboard, varnished, 3s. 6d. ; coloured sheet. Is. 6d. 
* The Maps of the Old Testament and New Testament can be had, mounted 
together, price 8s. 

and EPISTLES: showing St. Paul's Missionary Journeys, Journey to Rome, 
&c. Size, 22 inches by 17. Coloured and mounted on roller, varnished, 4s. ; 
on millboard, varnished, 3s. 6d. ; coloured sheet, Is. Gd. 

I'ENINSULA of SINAI, the NEGEB, and LOWER EGYPT, to illustrate 
the History of the Patriarchs and the Exodus; with a Supplementary Map of 
tne Migration of Terah and Abraham. Size, 17 inches by 22. Coloured and 
mounted on roller, varnished, 4s.; on millboard, 3s. 6d.; coloured sheet. 
Is. 6d. 

NORTH AMERICA.— Size, 27 inches by 32. Coloured and mounted on 
roller, varnished, 6s. ; coloured sheet, 2s. 6d. 

SOUTH AMERICA.— Size, 27 inches by 32. Coloured and mounted on 
roller, varnished, 6s.; coloured sheet, 2s. 6d. 

AUSTRALIA.— Size, 22 inches by 17. Coloured and mounted on roller, 
varnished, 4s. ; on millboard, varnished, 3s. 6d. ; coloured sheet. Is. 6d. 

NEW ZEALAND.— Size, 17 inches by 22. Coloured, and mounted on roller, 
varnished, 4s. ; on millboard, varnished, 3s. 6d. ; coloured sheet, Is. M. 

Edward Stanford, 55, Charing Cross, London. 



For use in Schools and Colleges. Edited by Professor Ramsay, LL.D., F.K.S., &c., 
Dtrector-Oeneral of the Geological Surveys of the United Kingdom. 

This series aims at exhibiting in the first place, and prominently, the forms of 
relief and of contour of the land masses of the globe, and ne.\t of the sea bed. At 
once a general idea is gained by the youngest student, on an inspection of the Map, 
of the relative position of the high, dry, and cold table-lands and mountainous 
regions, and the warm, moist, and fertile plains in each great division of the globe. 
For instance, in our own country it is seen at once why the eastern part is devoted 
to agrtcullural purposes, and the western part to mining and manufacturing ; or by 
reference to the Map of P^urope we can readily see how a rise in the level of the sea 
of a few hundreds of feet would suffice to Inundate the whole northern part of 
Europe ; and on the otlier hand, how the general upheaval of the land of a few hun- 
dreds of feet would alt^r the whole contour of Europe, connecting the British Jsles 
with the Continent, and annihilating the Xorth Sea and the Baltic. 

The following Maps, forming part of the Physical .Series of Wall Maps for use in 
Schools and Colleges, are ready for sale, and will be found, both in utility and artistic 
finish, not inferior to any Maps hitherto offered to the public. 

They are uniform in scale and size with the Political Series already In use, and 
•which have acquired so great a popularity; and wiU be found as accurate and, it is 
hi ped and believed, as useful in teaching Physical Geography as the companion series 
are and have been in Political Geography. 

BRITISH ISLES. Mounted on linen, on rollers, varnished. Scale, Hi miles 
to an inch ; size, 50 inches by 58. Price 30«. 

ENGLAND and "WALES. Mounted on linen, on rollers, varnished. Scale, 
s miles to an inch ; size, 50 inches by 58. Price 30«. 

SCOTLAND. Mounted on linen, on rollers, varnished. Scale, 8 miles to an 
inch; size, 34 inches by 42. Price l»s. 

IRELAND. Mounted on linen, on rollers, varnished. Scale, 8 miles to an inch ; 
siz'j, 3-1 inches by 43. Price Iss. 

EUROPE. Mounted on linen, on rollers, varnished. Scale, 65 miles to an inch ; 
size, S-i inches by 50. Price 30s. 

ASIA. Mounted on linen, on rollers, varnished. Scale, 140 miles to an inch ; 
size, 58 inches by 50. Price 30«. 

AFRICA. Mounted on linen, on rollers, varnished. Scale, 116 miles to an inch; 

size, 50 inches by 5s. Price 30s. 


miles to an inch ; size, 50 inches by 1 

SOUTH AMERICA. Jlounted on linen, on rollers, varnished. Scale, 97 
miles to an inch ; size, 50 inches by 58. Price 30s. 

Edward Stanford, 55, Cliaring Cross, London. 


MAPS, for class teaching, constructed by Akrowsmith, Walker, &c. New 
and revised editions, coloured, mounted, and varnished. 

The World in Hemispheres. Size, 51 inches by 26. Price 12s. 

The World (Mercator). Size, 50 inches by 32. Price 10s. 

The British Isles. Size, 51 inches by 41. Price 10s. 

Also the following, each 6s., size, 34 inches by 26 : — 
Europe. Australia. Journeyings of 

Asia. I Eng-land. the Children of 

Africa. Scotland. Israel. 

America. Ireland. S. Paul's Voyages 

New Zealand. Roman Empire. and Travels. 

Price, in plain sheet, 2s. 
inches by 4 feet 3 inches. Price, in plaii 


coloured, 3s. ; mounted on rollers, 7s. 

The World (globular). 2 feet 

sheet. Is.; coloured. Is. 6rf. 
The World (Jlercator), 21 inches by 15 In. 
And the following, plain sheet. Is. 3d. ; coloured, Is. 6d. ; mounted on rollers, 4s. ; 

size, 2 feet 10 inches by 2 feet 2 inches. 

Europe. I America. Ireland. 

Asia. Eng-land. Palestine (O. Test.). 

Africa. Scotland. ' Palestine (N. Test.). 

STANFORD'S OUTLINE MAPS. Size, 17 inches by 14. printed on 
drawing paper. A Series of Ueograiihical E.\ercises, to be filled in from the 
Useful Knowledge Society's Alaps and Atlases. Price 6d. each. 

World in Hemi- Germany, General, 
spheres, West. | Italy, General. 

World in Hemi- 
spheres, East. 
British Isles. 

Spain an 

Turkish Empire. 

Asia Minor. 








America, North. 

Canada, and the 

United States. 
America, South. 
West India Islands 
New Zealand. 


Price 3d. each. 

Uniform in size, price, &c., 
Size, 16 inches by 14. 

Edward Stanford, 55, Charing Cross, London. 


giagrams of Hatural Ijistorn. 

These Diagrams, compiled by the eminent Scientific Men whose names are 
appended, are drawn witli tlie strictest regard to Nature, and engraved in the best 
style of art. The Series coni^ists of Eleven Subjects, each arranged so that it may be 
mounted in one sheet, or be divided into four sections and fielded in the form of a 
boolc, thus rendering them available either for Class Exercises or Individual Study. 

Price of each, mounted on roller and varnished, 6s. ; or folded in booli form, 4s. 

F.R.G.S. Exliibits nearly 600 of the more prominent forms of Organic remains 
found in British Strata. 


By J. W. LowKv. F.Pt.G5. This Diagram is similarly arranged to No. 1, and 
illustrates upwards of »00 specimens of the Tertiary Formation. 

in. FOSSIL CRUSTACEA. By J. W. Salter, A.L.S., F,G.S., and H. 
WooiiWAiiD, F.G.S., F.Z.S. Consisting of about 500 Illustrations of the Orders 
and Sub-Orders, and showing their Range in Geological time. 

IV. The VEGETABLE KINGDOM. By A. Hesfret. Arranged 
according to tlie Natural System, each Order being illustrated by numerous 
examples of representative species. 


Woodward. Represented in six classes : Cephulapoda, illustrated by 20 
examples; Gasteropoda, 4 Orders, illustrated by l¥0 examples; Pteropoda, 
illustrated by 1* examples; Ojnehifera, illustrated by 158 examples; Brachio- 
poda, illustrated by 11 examples; and Tunicata, illustrated by 20 examples. 

NELIDA-and ENTOZOA. By Adam White and Dr. Baird. The 
numerous Tribes represented under these Orders are illustrated by upwards of 
180 examples, including Centipedes, Spiders, Crabs, Sandhoppers, Seamice, 
Serpulas, Leeches, Jcc. 

VIL INSECTS. By Adam White. Contains nearly 250 drawings of the 
different Orders: Coleoptera; Euplexoptera ; Orthoptera ; Thysanijptera — 
Thripid*, &c. ; Xeuroptera; Trichoptera; Hymeiioptera ; Sirepsiptera — 
Hylechihrus rubis ; Lepidoplera; Homoptera — Heteroptera ; Diptera; and 


VIII. FISHES. By P. H. Gosse. Showing over 130 of the most conspicuous 
types, arranged in their Orders and Families. 

IX. REPTILIA and AMPHIBIA. By Drs. Bell and Baird. Contains 

1115 figures of the principal typical forms. 

X. BIRDS. By George Gray. Contains drawings of 236 of the leading illus- 

trative si)ecimen8. 

XI. MAMMALIA. By Dr. Baird. Exhibits 145 of the chief iUustrations 
selected from the several Orders. 

Edward Stanford, 55, Charing Cross, London. 


gocks for (Lmh. 

Edited by the Rev. J. P. Faunthorpe, M.A., Principal of "SVhitelands Training 

College. With original Illustrations. Post 8vo, cloth. 
Standard 1.— Illustrated Short Stories, &c. 56 pp. 4d. 

„ 2.— Illustrated Easy Lessons. 164 pp. is. 3d. 

,, 3.— Instructive Lessons. Illustrated. 206 pp. is.Gd. 

„ 4,— Orig-inal Stories and Selected Poems. 264 pp. it.9d. 

,, 5.— Domestic Economy and Household Science. 

356 pp. 2s. 6d. 

„ 6.— Literary Reader. 

gates^a Smcs of <itantiurtr |Uabinig- 
§00 lis for §ons. 

Edited by the Rev. Evan Daniel, M.A., Principal of the Battersea Training 
College. Post 8vo, cloth. 

Standard I. 88 pp. Price sd. 
„ II. 110 pp. Price is. 
,, III. 184 pp. Price Is. 6d. 

Standard IV. 
„ VI. 

n §a.ttersjja prhmrs, for Jious anb (bxxh. 

Written by the Rev. E. Daniel, M.A. 
Primer I. Illustrated. Large type. 42 pp. Price 5d. 
„ II. „ 64 pp. Price 7d. 

Simple Iftssons. 

Chiefly intended for Elementary Schools, and for Home Use. 
Our Bodily Life— How and Why We Breathe— Food— Drink- 
Cookery— Needlework— Clothing'— Air and Ventilation- 
Sicknesses that Spread— Weather — Astronomy— Birds — 
Flowers — Money. 


Sirs. Fenwtck Miller ; G. Phillips Bevan, F.G.S. ; Dr. Mann, F.R.A.S., 
K.R.G.S. ; J. C. Bdckmaster, B.A. ; Mrs. Benjamin Clarke; J. J. Pope; 
Richard A. Proctor, B.A. ; Kev. F. 0. Morris, M.A. ; Rev. G. Henslow, M.A., 
^.L.S. ; Rev. T. E. Crallan, M.A. 

Price 16s. per 100. Single copies 3d. each. 

Edward Stanford, 55, Charing' Cross, London. 


Irbing's Improbcir Cutccbisms. 

Edited by ROBERT JAMES MAXN, M.D.. F.R.A.S., F.R.G.S., late Super- 
intendent of Education in Natal. Price 9d. each. 




British Constittition. 


Classical Biography. 

English Grammar. 

English History. 

French Grammar. 

French History. 

Grecian Antiquities. 
Grecian History. 
Irish History. 
Italian Grammar. 
Jewish Antiquities. 

Natural Philosophy. 
Roman Antiquities. 
Roman History. 
Sacred History. 

General Geography. | Scottish History. 

General Knowledge. j Universal History. 

.Stunforb's ^Icmcntarn ^tlascs. 


taiijing Sixteen Coloured .Maps, each 17 inches bj' 14. 

ELEMENTARY PHYSICAL ATLAS, intended chiefly for Map- 
Drawing, and ihe Study of the Great Physical Features and Relief Contours of 
the Continent, with an Introduction to serve as a Guide for both purposes. By 
the Rev. J. P. Faunthoepe, M.A., F.R.G.S., Principal of AVhilelands Training 
College. Eighth Edition. Sixteen Maps, printed In Colour, with descriptive 
Letterpress. Price 4s. 

OUTLINE ATLAS.— Containing Sixteen Maps, Intended chiefly for use with 
the ' Elementary Physical Atlas.' Coloured Wrapper, Is. 

PROJECTION ATLAS.— Containing Sixteen Plates of Projections, intended 
chiefly for use with the ' jilementary Physical Atlas.' Coloured Wrapper, Is. 

BLANK SHEETS for MAPS.— Sixteen Leaves of Blank Paper for Map- 
Drawing, intended chiefly lor use with the 'Elementary Physical Atlas. 
Coloured Wrapper, 6d. 

PHYSICAL ATLAS.— A Series of Twelve Maps for Map-Drawing and 
Examination. By Chakles Bird, BA., F.R.A.S., Science Master in the Brad- 
ford Grammar School. Royal 4io, stiff boards, cloth back, 4s. 6d. 

I Edward Stanford, 55, Charing Cross, London. 


Scripture anb gmmal ^rhxts. 

of Fifty-two Prints to aid Scriptural Instruction, selected in part by the Autiior 
of ' Lessons on Objects.' Ttie whole from Original Designs by S. Bendixen, 
Artist, expressly for this Work. They have been recently re-eneraved, and are 
carefully coloured. Size, ITJ inches by 13. • 

Price of the Work. 

The Set of 52 Prints, In Paper Wrapper 52s. 

in One Volume, handsomely half-bound . . . . 60s. 

In Varty's Oak Frame, with glass, lock and key 60s. 

Single Prints, Is. each ; mounted on millboard, Is. id. each. 


ANIMALS, Drawn from Nature and from the Works of Eminent Artists. In 
36 carefully-coloured Plates, exhibiting 130 Figures. Size, 12 inches by 9. 
The selection of Animals lias been limited to those which are most known and 
best adapted to elicit inquiry from the youug, and alford scope for instruction and 

Bound In Frame 

in Cloth. and Glass. 

Set of 36 Prints, Coloured 18s. . . 24s. . . 24s. 

Plain.. .. .. .. 12s. .. 17s. .. 18s. 

Single Prints, coloured, 6d. ; mounted on millboard, lOd. 

The ANIMAL KINGDOM at ONE VIEW, clearly exhibiting, on 
four beautifully-coloured Plates containing 184 Illustr.itlons, the relative sizes of 
Animals to Man, and their comparative sizes with each other, as arranged in 
Divisions, Orders, &c., according to the method of Baron Cuvier. 
Exhibited on four Imperial Sheets, each 30 inches by 22 : — 

Rollers, and 

Complete Set, 

Animals and L.wdscape,/«i; coloured 
Animals only coloured 

Single Plates,/uJt coloured .. .. 


showing their Utility to Man, in their Services during Life and Uses after 
Death. Beautifully coloured. Size, 15 inches by 12. Price, the set, 31s. 6d. ; 
in frame, with glass, lock and key, 39s. ed. ; or half-bound in leather, and 
lettered, 1 vol. folio, 42s. 

The 21 separate Prints may also be had, price Is. 6d. each. 
Or Mounted on Millboard, Is. lOd. 

For complete lists of Edwakd Stanford's PnBLiCATiONS, see his General 
Catalogue of Maps and Atlases, List of Books, Edhcational Catalogue, &c., 
gratis on application, or by post for one penny stamp. 

Edward Stanford, 55, Charing Cross, London. 





1. ATLASES and MAPS.— General Catalogue of Atlases and Maps 

Iiublished or sold by Edwabd Stanfokd. New Edition. 

2. BOOKS.— -Selected List of Books published by Edwarp Stanford. 

Naval and Jlilitary Books, Ordnance Sun-ey Publications, Memoirs of the 
Geological Survey of the United Kingdom, and Jleteorologlcal Office 
Publications, published on account of Her Majesty's Stationery Office. 

4. LONDON and its ENVIRONS.— Selected List of Maps of 

London and its Environs, published by Edward Staxford. 

5. ORDNANCE MAPS.— Catalogue of the Ordnance Maps, published 

under the superintendence of Culonel Cooke. Price 6d. ; per post Td. 


IRELAND. — Catalogue of the Geological Maps, Sections, and Memoirs of 
the Geological Survey of Great Britain and Ireland, under the Superin- 
tendence of Andrew C. Ramsat, LL.D., F.R.S.. Director-General of the 
Geological Surveys of the United Kingdom. Price 6d.; per post Id. 

8. ADMIRALTY CHARTS.— Catalogue of Charts, Plans, Views, and 

Sailing 1 lirections. &c., published by order of the Lords Commissioners of 
the Admiralty. 224 pp. royal 8vo. Price 7s. ; per post Is. id. 

9. INDIA.— Catalogue of Maps of the British Possessions in India and 

other parts of Asia, with continuation to the year 1876. Published by 
order of Her Majesty's Secretary of State for India, in Council Post free 
for Two Penny Stamps. 

10. EDUCATIONAL.— -Select List of Educational Work>% published by 

Edward .Stanford, including those formerly published by Vauti and 


ford's Catalogue ot .School Stationery, Educational Works, Atlases, Maps, 
and Globes, with Specimens of Copy and Exercise Books, &c. 

12. SCHOOL PRIZE BOOKS.— List of Works specially adapted for 

School Prizes, Awards, and Presentations. 
14. BOOKS and MAPS for TOURISTS.— Stanford's Tourist's 

Cat ilogue, containing a List, irrespective of Publisher, of all the best 

Guide Books and Maps suitable for the British and Continental Traveller ; 

with Index Maps to the Government Surveys of England, France, and 

%* With the exception of those with price affixed, any of the above Cata- 
logues can be had gratis on Applicaiion ; or, per post, for I'euuy Stamp. 

Edward Stanford, 55, Charing Cross, London. 

Agent, by Appointment, for the sale of the Ordnance and Geological 
Survey Maps, the Admiralty Charts, Her Majesty's Stationery 
Office and India Office Publications, ^c. 

^^^Sri t%^i}^xjv%